Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Summary Collateral Information
	Description
Group 1
Pool 8075	OPTION ARM
Pool 8076	OPTION ARM

General Information
Description	Total	Pool 8075	Pool 8076	Group 1
Weighted Average Pass Through Rate	6.34592%	6.39124%	6.03139%	6.34592%
Weighted Average Mortgage Interest Rate	7.92126%	7.97254%	7.56542%	7.92126%
Weighted Average Remaining Term (in Months)	403.06014	402.16627	409.30076	403.06014
Weighted Average Loan Age (in Months)	6.10594	6.10550	6.10899	6.10594
Average Ending Scheduled Principal Balance	$516,134.96	$514,648.34	$526,758.21	$516,134.96
Remaining Loan Count	3071	2694	377	3071
Ending Scheduled Principal Balance	$1,585,050,471.51	$1,386,462,624.65	$198,587,846.86	$1,585,050,471.51

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Geographic Distribution
Total			Pool 8075			Pool 8076
State	Percent	Ending Scheduled Principal Balance	State	Percent	Ending Scheduled Principal Balance	State	Percent	Ending Scheduled Principal Balance
CA	$918,502,048.22	57.95%	CA	$769,445,896.66	55.50%	CA	$149,056,151.56	75.06%
FL	$182,645,465.91	11.52%	FL	$174,845,527.83	12.61%	FL	$7,799,938.08	3.93%
NY	$65,295,384.67	4.12%	NY	$63,855,759.35	4.61%	AZ	$5,135,503.34	2.59%
WA	$61,782,719.99	3.90%	WA	$57,681,155.82	4.16%	MA	$4,338,544.13	2.18%
AZ	$37,302,764.14	2.35%	NJ	$33,279,189.30	2.40%	VA	$4,255,492.53	2.14%
OTHER	$319,522,088.58	20.16%	OTHER	$287,355,095.69	20.73%	OTHER	$28,002,217.22	14.10%

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Geographic Distribution
Group 1
State	Percent	Ending Scheduled Principal Balance
CA	$918,502,048.22	57.95%
FL	$182,645,465.91	11.52%
NY	$65,295,384.67	4.12%
WA	$61,782,719.99	3.90%
AZ	$37,302,764.14	2.35%
OTHER	$319,522,088.58	20.16%

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Prepayment Information (all groups)
	1 Month	3 Month	6 Month	12 Month	Cumulative
PSA	494.70361%	696.25903%	1105.65154%	1105.65154%	1105.65407%
CPR	6.04126%	7.10909%	7.97263%	7.97263%	7.97265%
SMM	0.51794%	0.61265%	0.68998%	0.68998%	0.68998%

Trigger Events
	Trigger Flag
Optional Termination Date Has Occurred; 1=Yes, 0=No	0
Senior Prepayment Step-Down Has Occurred; 1=Yes, 0=No	0
Senior Credit Support Depletion Date Has Occurred; 1=Yes, 0=No	0

Comments

1. The Class B Certificates provide, to the limited extent described in the Prospectus Supplement, credit support, to certain Senior Certificates. The "Prospectus Supplement" is that certain Prospectus Supplement, dated April 24, 2007 to that certain Prospectus Supplement, dated April 17, 2007, to which certain Senior Certificates were offered.

2. The MBA method of delinquency calculation is used.

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Certificate Payment Summary Report
Class	CUSIP	Original Principal/Notional Balance	Beginning Principal/Notional Balance	Interest Distribution	Principal Distribution	Principal Loss	Deferred Interest	Total Distribution	Ending Principal/Notional Balance
1A	93364CAA6	$750,761,000.00	$730,528,975.49	$3,502,478.70	$766,698.02	$0.00	$0.00	$4,269,176.72	$729,762,277.47
1A1B	93364CAB4	$250,255,000.00	$243,510,955.91	$1,167,499.12	$255,567.37	$0.00	$0.00	$1,423,066.49	$243,255,388.54
2A	93364CAC2	$144,003,000.00	$140,291,905.12	$646,161.16	$1,078,297.95	$0.00	$0.00	$1,724,459.11	$139,213,607.17
CA1B	93364CAD0	$143,129,000.00	$139,293,061.51	$623,481.58	$262,576.12	$0.00	$0.00	$886,057.70	$139,030,485.39
CA1B_GRP1	XXXXXXXXX	$125,128,000.00	$121,755,964.47	$544,984.77	$127,784.19	$0.00	$0.00	$672,768.96	$121,628,180.28
CA1B_GRP2	XXXXXXXXX	$18,001,000.00	$17,537,097.04	$78,496.78	$134,791.92	$0.00	$0.00	$213,288.70	$17,402,305.12
CA1C	93364CAE8	$143,129,000.00	$139,293,061.51	$632,767.78	$262,576.12	$0.00	$0.00	$895,343.90	$139,030,485.39
CA1C_GRP1	XXXXXXXXX	$125,128,000.00	$121,755,964.47	$553,101.83	$127,784.19	$0.00	$0.00	$680,886.02	$121,628,180.28
CA1C_GRP2	XXXXXXXXX	$18,001,000.00	$17,537,097.04	$79,665.92	$134,791.92	$0.00	$0.00	$214,457.84	$17,402,305.12
1XPPP	93364CAF5	$0.00	$67,531.74	$793,496.81	$67,531.74	$0.00	$0.00	$861,028.55	$0.00
1XPPP_NOTIONAL	XXXXXXXXX	$1,421,901,169.00	$1,387,808,107.53	$793,496.78	$0.00	$0.00	$0.00	$793,496.78	$1,386,462,624.65
1XPPP_PRINCIPAL	XXXXXXXXX	$0.00	$67,531.74	$0.00	$67,531.74	$0.00	$0.00	$67,531.74	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Certificate Payment Summary Report (Continued)
Class	CUSIP	Original Principal/Notional Balance	Beginning Principal/Notional Balance	Interest Distribution	Principal Distribution	Principal Loss	Deferred Interest	Total Distribution	Ending Principal/Notional Balance
2XPPP	93364CAG3	$0.00	$55,352.44	$102,080.44	$55,352.44	$0.00	$0.00	$157,432.88	$0.00
2XPPP_NOTIONAL	XXXXXXXXX	$204,551,860.00	$199,991,132.87	$102,080.44	$0.00	$0.00	$0.00	$102,080.44	$198,587,846.86
2XPPP_PRINCIPAL	XXXXXXXXX	$0.00	$55,352.44	$0.00	$55,352.44	$0.00	$0.00	$55,352.44	$0.00
B1	93364CAH1	$32,530,000.00	$32,460,409.81	$150,974.73	$28.19	$0.00	$0.00	$151,002.92	$32,460,381.62
B2	93364CAJ7	$36,595,000.00	$36,516,713.71	$171,362.30	$31.71	$0.00	$0.00	$171,394.01	$36,516,682.00
B3	93364CAK4	$12,199,000.00	$12,172,903.15	$59,457.02	$10.57	$0.00	$0.00	$59,467.59	$12,172,892.58
B4	93364CAL2	$52,859,000.00	$52,745,920.74	$278,289.69	$45.81	$0.00	$0.00	$278,335.50	$52,745,874.93
B5	93364CAM0	$19,518,000.00	$19,476,245.88	$102,757.48	$16.91	$0.00	$0.00	$102,774.39	$19,476,228.97
B6	93364CAN8	$8,132,000.00	$8,114,603.52	$42,812.99	$7.05	$0.00	$0.00	$42,820.04	$8,114,596.47
B7	93364CAP3	$7,319,000.00	$7,303,342.74	$38,532.74	$6.34	$0.00	$0.00	$38,539.08	$7,303,336.40
B8	93364CAR9	$5,693,000.00	$5,680,821.18	$29,972.25	$4.93	$0.00	$0.00	$29,977.18	$5,680,816.25
B9	93364CAS7	$5,692,000.00	$5,679,823.31	$29,966.98	$4.93	$0.00	$0.00	$29,971.91	$5,679,818.38
B10	93364CAT5	$14,638,929.00	$14,607,612.62	$77,070.65	$12.69	$0.00	$0.00	$77,083.34	$14,607,599.93

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Certificate Payment Summary Report (Continued)
Class	CUSIP	Original Principal/Notional Balance	Beginning Principal/Notional Balance	Interest Distribution	Principal Distribution	Principal Loss	Deferred Interest	Total Distribution	Ending Principal/Notional Balance
R	93364CAQ1	$100.00	$0.00	$0.21	$0.00	$0.00	$0.00	$0.21	$0.00
R_SYN	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
TFEE	XXXXXXXXX	$0.00	$0.00	$502.80	$0.00	$0.00	$0.00	$502.80	$0.00
YIELD_PAYMENTS	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
Total*		$1,626,453,029.00	$1,587,799,240.38	$8,449,162.63	$2,748,768.89	$0.00	$0.00	$11,197,931.52	$1,585,050,471.49

*Total balances exclude notional balances.

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Total Funds Available for Distribution
PRINCIPAL BALANCE
Scheduled Principal Received or Advanced	($5,503,601.45)
Unscheduled Principal	$970,026.93
Prepayments in Full	$7,282,343.41
Repurchases	$0.00
Liquidations	$0.00
Total Principal	$2,748,768.89
INTEREST
Accrued Interest at Gross Rate	$10,481,148.76
Relief Act Shortfall	$0.00
Prepayment Interest Shortfall	$0.00
Servicing Fees	$2,084,446.47
Other	$0.00
Total Interest	$8,396,702.63
ADDITIONAL FUNDS
Excess Liquidation Proceeds	$0.00
Subsequent Recoveries	$0.00
Prepayment Penalties	$52,460.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Total Funds Available for Distribution
ADDITIONAL FUNDS
Other	$0.00
Total Additional Funds	$52,460.00
Total Funds Available for Distribution	$11,145,471.52

Certificate Payment Report - Principal
Class	CUSIP	Beginning Principal/Notional Balance	Principal Distribution	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal Distribution	Ending Principal/Notional Balance
1A	93364CAA6	$730,528,975.49	$766,698.02	$0.00	$0.00	$0.00	$0.00	$766,698.02	$729,762,277.47
1A1B	93364CAB4	$243,510,955.91	$255,567.37	$0.00	$0.00	$0.00	$0.00	$255,567.37	$243,255,388.54
2A	93364CAC2	$140,291,905.12	$1,078,297.95	$0.00	$0.00	$0.00	$0.00	$1,078,297.95	$139,213,607.17
CA1B	93364CAD0	$139,293,061.51	$262,576.12	$0.00	$0.00	$0.00	$0.00	$262,576.12	$139,030,485.39
CA1B_GRP1	XXXXXXXXX	$121,755,964.47	$127,784.19	$0.00	$0.00	$0.00	$0.00	$127,784.19	$121,628,180.28
CA1B_GRP2	XXXXXXXXX	$17,537,097.04	$134,791.92	$0.00	$0.00	$0.00	$0.00	$134,791.92	$17,402,305.12
CA1C	93364CAE8	$139,293,061.51	$262,576.12	$0.00	$0.00	$0.00	$0.00	$262,576.12	$139,030,485.39
CA1C_GRP1	XXXXXXXXX	$121,755,964.47	$127,784.19	$0.00	$0.00	$0.00	$0.00	$127,784.19	$121,628,180.28
CA1C_GRP2	XXXXXXXXX	$17,537,097.04	$134,791.92	$0.00	$0.00	$0.00	$0.00	$134,791.92	$17,402,305.12

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Certificate Payment Report - Principal (Continued)
Class	CUSIP	Beginning Principal/Notional Balance	Principal Distribution	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal Distribution	Ending Principal/Notional Balance
1XPPP	93364CAF5	$67,531.74	$67,531.74	$0.00	$0.00	$0.00	$0.00	$67,531.74	$0.00
1XPPP_NOTIONAL	XXXXXXXXX	$1,387,808,107.53	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$1,386,462,624.65
1XPPP_PRINCIPAL	XXXXXXXXX	$67,531.74	$67,531.74	$0.00	$0.00	$0.00	$0.00	$67,531.74	$0.00
2XPPP	93364CAG3	$55,352.44	$55,352.44	$0.00	$0.00	$0.00	$0.00	$55,352.44	$0.00
2XPPP_NOTIONAL	XXXXXXXXX	$199,991,132.87	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$198,587,846.86
2XPPP_PRINCIPAL	XXXXXXXXX	$55,352.44	$55,352.44	$0.00	$0.00	$0.00	$0.00	$55,352.44	$0.00
B1	93364CAH1	$32,460,409.81	$28.19	$0.00	$0.00	$0.00	$0.00	$28.19	$32,460,381.62
B2	93364CAJ7	$36,516,713.71	$31.71	$0.00	$0.00	$0.00	$0.00	$31.71	$36,516,682.00
B3	93364CAK4	$12,172,903.15	$10.57	$0.00	$0.00	$0.00	$0.00	$10.57	$12,172,892.58
B4	93364CAL2	$52,745,920.74	$45.81	$0.00	$0.00	$0.00	$0.00	$45.81	$52,745,874.93
B5	93364CAM0	$19,476,245.88	$16.91	$0.00	$0.00	$0.00	$0.00	$16.91	$19,476,228.97
B6	93364CAN8	$8,114,603.52	$7.05	$0.00	$0.00	$0.00	$0.00	$7.05	$8,114,596.47
B7	93364CAP3	$7,303,342.74	$6.34	$0.00	$0.00	$0.00	$0.00	$6.34	$7,303,336.40

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Certificate Payment Report - Principal (Continued)
Class	CUSIP	Beginning Principal/Notional Balance	Principal Distribution	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal Distribution	Ending Principal/Notional Balance
B8	93364CAR9	$5,680,821.18	$4.93	$0.00	$0.00	$0.00	$0.00	$4.93	$5,680,816.25
B9	93364CAS7	$5,679,823.31	$4.93	$0.00	$0.00	$0.00	$0.00	$4.93	$5,679,818.38
B10	93364CAT5	$14,607,612.62	$12.69	$0.00	$0.00	$0.00	$0.00	$12.69	$14,607,599.93
R	93364CAQ1	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
R_SYN	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
TFEE	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
YIELD_PAYMENTS	XXXXXXXXX	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
Total *		$1,587,799,240.38	$2,748,768.89	$0.00	$0.00	$0.00	$0.00	$2,748,768.89	$1,585,050,471.49

*Total balances exclude notional balances.

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Certificate Payment Report - Interest
Class	Beginning Principal/Notional Balance	Interest Rate Accrued	Interest Rate Paid	Interest Accrued	Prepayment Interest Shortfall	Relief Act Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Total Interest Distributed	Total Carryforward Amount Remaining
1A	$730,528,975.49	5.7533300000%	5.7533300000%	$3,502,478.56	$0.00	$0.00	$0.00	$0.14	$0.00	$0.00	$3,502,478.70	$0.00
1A1B	$243,510,955.91	5.7533300000%	5.7533300000%	$1,167,499.07	$0.00	$0.00	$0.00	$0.05	$0.00	$0.00	$1,167,499.12	$0.00
2A	$140,291,905.12	5.5270000000%	5.5270000000%	$646,161.13	$0.00	$0.00	$0.00	$0.03	$0.00	$0.00	$646,161.16	$0.00
CA1B	$139,293,061.51	5.3712500000%	5.3712500000%	$623,481.55	$0.00	$0.00	$0.00	$0.03	$0.00	$0.00	$623,481.58	$0.00
CA1B_GRP1	$121,755,964.47	5.3712500000%	5.3712500000%	$544,984.77	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$544,984.77	$0.00
CA1B_GRP2	$17,537,097.04	5.3712500000%	5.3712500000%	$78,496.78	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$78,496.78	$0.00
CA1C	$139,293,061.51	5.4512500000%	5.4512500000%	$632,767.75	$0.00	$0.00	$0.00	$0.03	$0.00	$0.00	$632,767.78	$0.00
CA1C_GRP1	$121,755,964.47	5.4512500000%	5.4512500000%	$553,101.83	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$553,101.83	$0.00
CA1C_GRP2	$17,537,097.04	5.4512500000%	5.4512500000%	$79,665.92	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$79,665.92	$0.00
1XPPP	$67,531.74	13612.0354085339%	14099.9792986231%	$766,037.03	$0.00	$0.00	$0.00	$0.03	$0.00	$0.00	$793,496.81	$0.00
1XPPP_NOTIONAL	$1,387,808,107.53	0.6623714266%	0.6861151270%	$766,037.03	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$793,496.78	$0.00
1XPPP_PRINCIPAL	$67,531.74	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Certificate Payment Report - Interest (Continued)
Class	Beginning Principal/Notional Balance	Interest Rate Accrued	Interest Rate Paid	Interest Accrued	Prepayment Interest Shortfall	Relief Act Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Total Interest Distributed	Total Carryforward Amount Remaining
2XPPP	$55,352.44	1671.0474570993%	2213.0285132869%	$77,080.46	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$102,080.44	$0.00
2XPPP_NOTIONAL	$199,991,132.87	0.4625032759%	0.6125097960%	$77,080.46	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$102,080.44	$0.00
2XPPP_PRINCIPAL	$55,352.44	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
B1	$32,460,409.81	5.5812500000%	5.5812500000%	$150,974.72	$0.00	$0.00	$0.00	$0.01	$0.00	$0.00	$150,974.73	$0.00
B2	$36,516,713.71	5.6312500000%	5.6312500000%	$171,362.29	$0.00	$0.00	$0.00	$0.01	$0.00	$0.00	$171,362.30	$0.00
B3	$12,172,903.15	5.8612500000%	5.8612500000%	$59,457.02	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$59,457.02	$0.00
B4	$52,745,920.74	6.3312500000%	6.3312500000%	$278,289.68	$0.00	$0.00	$0.00	$0.01	$0.00	$0.00	$278,289.69	$0.00
B5	$19,476,245.88	6.3312500000%	6.3312500000%	$102,757.48	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$102,757.48	$0.00
B6	$8,114,603.52	6.3312500000%	6.3312500000%	$42,812.99	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$42,812.99	$0.00
B7	$7,303,342.74	6.3312500000%	6.3312500000%	$38,532.74	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$38,532.74	$0.00
B8	$5,680,821.18	6.3312500000%	6.3312500000%	$29,972.25	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$29,972.25	$0.00
B9	$5,679,823.31	6.3312500000%	6.3312500000%	$29,966.98	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$29,966.98	$0.00
B10	$14,607,612.62	6.3312500000%	6.3312727689%	$77,070.37	$0.00	$0.00	$0.00	$0.00	$0.00	$0.27	$77,070.65	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Certificate Payment Report - Interest (Continued)
Class	Beginning Principal/Notional Balance	Interest Rate Accrued	Interest Rate Paid	Interest Accrued	Prepayment Interest Shortfall	Relief Act Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Total Interest Distributed	Total Carryforward Amount Remaining
R	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.21	$0.00
R_SYN	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
TFEE	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$502.80	$0.00
YIELD_PAYMENTS	$0.00	0.0000000000%	0.0000000000%	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00	$0.00
Total *	$1,587,799,240.38			$8,396,702.07	$0.00	$0.00	$0.00	$0.34	$0.00	$0.27	$8,449,162.63	$0.00

*Total balances exclude notional balances.

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Principal Factors Report
Class	Original Scheduled Balance	Beginning Principal/Notional Balance	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal	Ending Principal/Notional Balance Percent	Ending Principal/Notional Balance
1A	$750,761,000.00	973.05131126	0.00000000	0.00000000	0.00000000	0.00000000	1.02122782	0.9720300834	972.03008344
1A1B	$250,255,000.00	973.05131130	0.00000000	0.00000000	0.00000000	0.00000000	1.02122783	0.9720300835	972.03008347
2A	$144,003,000.00	974.22904467	0.00000000	0.00000000	0.00000000	0.00000000	7.48802421	0.9667410205	966.74102046
CA1B	$143,129,000.00	973.19943205	0.00000000	0.00000000	0.00000000	0.00000000	1.83454171	0.9713648903	971.36489034
CA1B_GRP1	$125,128,000.00	973.05131122	0.00000000	0.00000000	0.00000000	0.00000000	1.02122778	0.9720300834	972.03008343
CA1B_GRP2	$18,001,000.00	974.22904505	0.00000000	0.00000000	0.00000000	0.00000000	7.48802400	0.9667410211	966.74102105
CA1C	$143,129,000.00	973.19943205	0.00000000	0.00000000	0.00000000	0.00000000	1.83454171	0.9713648903	971.36489034
CA1C_GRP1	$125,128,000.00	973.05131122	0.00000000	0.00000000	0.00000000	0.00000000	1.02122778	0.9720300834	972.03008343
CA1C_GRP2	$18,001,000.00	974.22904505	0.00000000	0.00000000	0.00000000	0.00000000	7.48802400	0.9667410211	966.74102105
1XPPP	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
1XPPP_NOTIONAL	$1,421,901,169.00	976.02290355	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.9750766473	975.07664729

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Principal Factors Report (Continued)
Class	Original Scheduled Balance	Beginning Principal/Notional Balance	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal	Ending Principal/Notional Balance Percent	Ending Principal/Notional Balance
1XPPP_PRINCIPAL	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
2XPPP	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
2XPPP_NOTIONAL	$204,551,860.00	977.70381003	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.9708435155	970.84351548
2XPPP_PRINCIPAL	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
B1	$32,530,000.00	997.86073809	0.00000000	0.00000000	0.00000000	0.00000000	0.00086658	0.9978598715	997.85987150
B2	$36,595,000.00	997.86073808	0.00000000	0.00000000	0.00000000	0.00000000	0.00086651	0.9978598716	997.85987157
B3	$12,199,000.00	997.86073859	0.00000000	0.00000000	0.00000000	0.00000000	0.00086646	0.9978598721	997.85987212
B4	$52,859,000.00	997.86073781	0.00000000	0.00000000	0.00000000	0.00000000	0.00086665	0.9978598712	997.85987117
B5	$19,518,000.00	997.86073778	0.00000000	0.00000000	0.00000000	0.00000000	0.00086638	0.9978598714	997.85987140
B6	$8,132,000.00	997.86073783	0.00000000	0.00000000	0.00000000	0.00000000	0.00086695	0.9978598709	997.85987088
B7	$7,319,000.00	997.86073781	0.00000000	0.00000000	0.00000000	0.00000000	0.00086624	0.9978598716	997.85987157
B8	$5,693,000.00	997.86073775	0.00000000	0.00000000	0.00000000	0.00000000	0.00086598	0.9978598718	997.85987177
B9	$5,692,000.00	997.86073612	0.00000000	0.00000000	0.00000000	0.00000000	0.00086613	0.9978598700	997.85986999

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Principal Factors Report (Continued)
Class	Original Scheduled Balance	Beginning Principal/Notional Balance	Principal Loss	Principal Reimbursed	Subsequent Recoveries	Deferred Interest	Total Principal	Ending Principal/Notional Balance Percent	Ending Principal/Notional Balance
B10	$14,638,929.00	997.86074651	0.00000000	0.00000000	0.00000000	0.00000000	0.00086687	0.9978598796	997.85987964
R	$100.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
R_SYN	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
TFEE	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000
YIELD_PAYMENTS	$0.00	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.0000000000	0.00000000

Interest Factors Report
Class	Original Balance	Interest Rate Accrued	Interest Rate Paid	Current Month Interest Accrued	Prepayment Interest Shortfall	Relief Act Interest Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Deferred Interest	Total Interest Distribution	Total Carryforward Amount Remaining
1A	$750,761,000.00	5.7533300000%	5.7533300000%	4.66523775	0.00000000	0.00000000	0.00000000	0.00000019	0.00000000	0.00000000	0.00000000	4.66523794	0.00000000
1A1B	$250,255,000.00	5.7533300000%	5.7533300000%	4.66523774	0.00000000	0.00000000	0.00000000	0.00000020	0.00000000	0.00000000	0.00000000	4.66523794	0.00000000
2A	$144,003,000.00	5.5270000000%	5.5270000000%	4.48713659	0.00000000	0.00000000	0.00000000	0.00000021	0.00000000	0.00000000	0.00000000	4.48713680	0.00000000
CA1B	$143,129,000.00	5.3712500000%	5.3712500000%	4.35608123	0.00000000	0.00000000	0.00000000	0.00000021	0.00000000	0.00000000	0.00000000	4.35608144	0.00000000

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Interest Factors Report (Continued)
Class	Original Balance	Interest Rate Accrued	Interest Rate Paid	Current Month Interest Accrued	Prepayment Interest Shortfall	Relief Act Interest Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Deferred Interest	Total Interest Distribution	Total Carryforward Amount Remaining
CA1B_GRP1	$125,128,000.00	5.3712500000%	5.3712500000%	4.35541821	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.35541821	0.00000000
CA1B_GRP2	$18,001,000.00	5.3712500000%	5.3712500000%	4.36068996	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.36068996	0.00000000
CA1C	$143,129,000.00	5.4512500000%	5.4512500000%	4.42096116	0.00000000	0.00000000	0.00000000	0.00000021	0.00000000	0.00000000	0.00000000	4.42096137	0.00000000
CA1C_GRP1	$125,128,000.00	5.4512500000%	5.4512500000%	4.42028826	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.42028826	0.00000000
CA1C_GRP2	$18,001,000.00	5.4512500000%	5.4512500000%	4.42563858	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.42563858	0.00000000
1XPPP	$0.00	13612.0354085339%	14099.9792986231%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
1XPPP_NOTIONAL	$1,421,901,169.00	0.6623714266%	0.6861151270%	0.53874140	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.55805340	0.00000000
1XPPP_PRINCIPAL	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
2XPPP	$0.00	1671.0474570993%	2213.0285132869%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
2XPPP_NOTIONAL	$204,551,860.00	0.4625032759%	0.6125097960%	0.37682600	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.49904430	0.00000000
2XPPP_PRINCIPAL	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
B1	$32,530,000.00	5.5812500000%	5.5812500000%	4.64109192	0.00000000	0.00000000	0.00000000	0.00000031	0.00000000	0.00000000	0.00000000	4.64109222	0.00000000
B2	$36,595,000.00	5.6312500000%	5.6312500000%	4.68266949	0.00000000	0.00000000	0.00000000	0.00000027	0.00000000	0.00000000	0.00000000	4.68266976	0.00000000

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Interest Factors Report (Continued)
Class	Original Balance	Interest Rate Accrued	Interest Rate Paid	Current Month Interest Accrued	Prepayment Interest Shortfall	Relief Act Interest Shortfall	Other Interest Shortfall	Unscheduled Interest	Interest Reimbursed	Carryforward Amount Paid	Deferred Interest	Total Interest Distribution	Total Carryforward Amount Remaining
B3	$12,199,000.00	5.8612500000%	5.8612500000%	4.87392573	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	4.87392573	0.00000000
B4	$52,859,000.00	6.3312500000%	6.3312500000%	5.26475491	0.00000000	0.00000000	0.00000000	0.00000019	0.00000000	0.00000000	0.00000000	5.26475510	0.00000000
B5	$19,518,000.00	6.3312500000%	6.3312500000%	5.26475459	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	5.26475459	0.00000000
B6	$8,132,000.00	6.3312500000%	6.3312500000%	5.26475529	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	5.26475529	0.00000000
B7	$7,319,000.00	6.3312500000%	6.3312500000%	5.26475475	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	5.26475475	0.00000000
B8	$5,693,000.00	6.3312500000%	6.3312500000%	5.26475496	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	5.26475496	0.00000000
B9	$5,692,000.00	6.3312500000%	6.3312500000%	5.26475404	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	5.26475404	0.00000000
B10	$14,638,929.00	6.3312500000%	6.3312727689%	5.26475468	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00001844	0.00000000	5.26477381	0.00000000
R	$100.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	2.10000000	0.00000000
R_SYN	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
TFEE	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000
YIELD_PAYMENTS	$0.00	0.0000000000%	0.0000000000%	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000	0.00000000

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Pool 8075
LOAN COUNT
Original Loan Count	2785
Beginning Loan Count	2701
Loans Added	0
Loans Prepaid-in-full	7
Loans Liquidated-in-full	0
Loans Repurchased	0
Ending Loan Count	2694
PRINCIPAL BALANCE
Original Scheduled Principal Balance	$1,421,901,168.74
Beginning Scheduled Principal Balance	$1,387,808,107.53
Scheduled Principal Received or Advanced	($4,858,967.45)
Unscheduled Principal	$941,183.11
Prepayments-in-full	$5,263,267.22

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Pool 8075 (Continued)
PRINCIPAL BALANCE
Liquidations-in-full	$0.00
Repurchases	$0.00
Principal Losses	$0.00
Ending Scheduled Principal Balance	$1,386,462,624.65
INTEREST
Accrued Interest at Gross Rate	$9,220,301.31
Unscheduled Interest	$0.30
Uncollected Interest	$0.00
Relief Act Shortfall	$0.00
Prepayment Interest Shortfall	$0.00
Other Interest Shortfall	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Pool 8075 (Continued)
FEES
Servicing Fees	$1,828,785.90
Other Fees	$0.00
ADDITIONAL FUNDS
Excess Liquidation Proceeds	$0.00
Subsequent Recoveries	$0.00
Prepayment Penalties	$27,460.00
Other	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Pool 8076
LOAN COUNT
Original Loan Count	393
Beginning Loan Count	379
Loans Added	0
Loans Prepaid-in-full	2
Loans Liquidated-in-full	0
Loans Repurchased	0
Ending Loan Count	377
PRINCIPAL BALANCE
Original Scheduled Principal Balance	$204,551,860.39
Beginning Scheduled Principal Balance	$199,991,132.87
Scheduled Principal Received or Advanced	($644,634.00)
Unscheduled Principal	$28,843.82
Prepayments-in-full	$2,019,076.19

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Pool 8076 (Continued)
PRINCIPAL BALANCE
Liquidations-in-full	$0.00
Repurchases	$0.00
Principal Losses	$0.00
Ending Scheduled Principal Balance	$198,587,846.86
INTEREST
Accrued Interest at Gross Rate	$1,260,847.45
Unscheduled Interest	$0.04
Uncollected Interest	($3,496.61)
Relief Act Shortfall	$0.00
Prepayment Interest Shortfall	$0.00
Other Interest Shortfall	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Pool 8076 (Continued)
FEES
Servicing Fees	$255,660.57
Other Fees	$0.00
ADDITIONAL FUNDS
Excess Liquidation Proceeds	$0.00
Subsequent Recoveries	$0.00
Prepayment Penalties	$25,000.00
Other	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Group 1
LOAN COUNT
Original Loan Count	3178
Beginning Loan Count	3080
Loans Added	0
Loans Prepaid-in-full	9
Loans Liquidated-in-full	0
Loans Repurchased	0
Ending Loan Count	3071
PRINCIPAL BALANCE
Original Scheduled Principal Balance	$1,626,453,029.13
Beginning Scheduled Principal Balance	$1,587,799,240.40
Scheduled Principal Received or Advanced	($5,503,601.45)
Unscheduled Principal	$970,026.93
Prepayments-in-full	$7,282,343.41

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Group 1 (Continued)
PRINCIPAL BALANCE
Liquidations-in-full	$0.00
Repurchases	$0.00
Principal Losses	$0.00
Ending Scheduled Principal Balance	$1,585,050,471.51
INTEREST
Accrued Interest at Gross Rate	$10,481,148.76
Unscheduled Interest	$0.34
Uncollected Interest	($3,496.61)
Relief Act Shortfall	$0.00
Prepayment Interest Shortfall	$0.00
Other Interest Shortfall	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Group 1 (Continued)
FEES
Servicing Fees	$2,084,446.47
Other Fees	$0.00
ADDITIONAL FUNDS
Excess Liquidation Proceeds	$0.00
Subsequent Recoveries	$0.00
Prepayment Penalties	$52,460.00
Other	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Total
LOAN COUNT
Original Loan Count	3178
Beginning Loan Count	3080
Loans Added	0
Loans Prepaid-in-full	9
Loans Liquidated-in-full	0
Loans Repurchased	0
Ending Loan Count	3071
PRINCIPAL BALANCE
Original Scheduled Principal Balance	$1,626,453,029.13
Beginning Scheduled Principal Balance	$1,587,799,240.40
Scheduled Principal Received or Advanced	($5,503,601.45)
Unscheduled Principal	$970,026.93
Prepayments-in-full	$7,282,343.41

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Total (Continued)
PRINCIPAL BALANCE
Liquidations-in-full	$0.00
Repurchases	$0.00
Principal Losses	$0.00
Ending Scheduled Principal Balance	$1,585,050,471.51
INTEREST
Accrued Interest at Gross Rate	$10,481,148.76
Unscheduled Interest	$0.34
Uncollected Interest	($3,496.61)
Relief Act Shortfall	$0.00
Prepayment Interest Shortfall	$0.00
Other Interest Shortfall	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Collateral Report Total (Continued)
FEES
Servicing Fees	$2,084,446.47
Other Fees	$0.00
ADDITIONAL FUNDS
Excess Liquidation Proceeds	$0.00
Subsequent Recoveries	$0.00
Prepayment Penalties	$52,460.00
Other	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Delinquency Information by Group*
Group ID	1 Month Count	Scheduled Ending Balance	2 Months Count	Scheduled Ending Balance	3 Months Count	Scheduled Ending Balance	4+ Months Count	Scheduled Ending Balance
Pool 8075	92	$54,033,580.88	11	$4,765,549.25	1	$1,218,217.99	2	$1,521,303.58
Pool 8076	9	$3,897,596.03	3	$1,221,571.05	1	$703,432.97	0	$0.00
Group 1	101	$57,931,176.91	14	$5,987,120.30	2	$1,921,650.96	2	$1,521,303.58
Aggregate	101	$57,931,176.91	14	$5,987,120.30	2	$1,921,650.96	2	$1,521,303.58

* Does not include mortgage loans in foreclosure or REO.

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Foreclosure, REO, and Bankruptcy by Group**
Group ID	Foreclosure Count	Scheduled Ending Balance	REO Count	Scheduled Ending Balance	Bankruptcy Count	Scheduled Ending Balance
Pool 8075	14	$9,829,961.06	1	$94,738.61	1	$140,814.62
Pool 8076	3	$1,284,024.74	0	$0.00	0	$0.00
Group 1	17	$11,113,985.80	1	$94,738.61	1	$140,814.62
Aggregate	17	$11,113,985.80	1	$94,738.61	1	$140,814.62

** Loans in Bankruptcy will also be reflected under their applicable delinquency or foreclosure status.

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Aggregate Loss Amount by Group
Group ID	Count	Loss Amount
Pool 8075	0	$0.00
Pool 8076	0	$0.00
Group 1	0	$0.00
Aggregate	0	$0.00

Servicer Advances by Group
Group	Count	Total
Pool 8075	2289	$2,379,112.22
Pool 8076	336	$349,781.84
Group 1	2625	$2,728,894.06
Aggregate	2625	$2,728,894.06

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Stop Advances Loans
Group	Count	Loan Balance	Total Scheduled P&I
Pool 8075	0	$0.00	$0.00
Pool 8076	0	$0.00	$0.00
Group 1	0	$0.00	$0.00
Aggregate	0	$0.00	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Delinquency Roll Rates-Aggregate***
Current Value	Current		1 Month		2 Months		3 Months
Prior Value	Count	Balance	Count	Balance	Count	Balance	Count	Balance
Current	2905	$1,490,432,441.26	88	$52,043,486.98	0	$0.00	0	$0.00
Delq 1 Month	27	$15,251,241.34	12	$5,644,604.80	12	$5,257,491.52	0	$0.00
Delq 2 Month	2	$796,812.75	0	$0.00	2	$729,628.78	2	$1,921,650.96
Delq 3 Month	0	$0.00	1	$243,085.13	0	$0.00	0	$0.00
Delq 4 Month	0	$0.00	0	$0.00	0	$0.00	0	$0.00
Foreclosure	0	$0.00	0	$0.00	0	$0.00	0	$0.00

Current Value	4+ Months		Foreclosure		REO
Prior Value	Count	Balance	Count	Balance	Count	Balance
Current	0	$0.00	0	$0.00	0	$0.00
Delq 1 Month	0	$0.00	0	$0.00	0	$0.00
Delq 2 Month	0	$0.00	11	$6,910,114.53	0	$0.00
Delq 3 Month	1	$901,082.00	0	$0.00	0	$0.00
Delq 4 Month	1	$620,221.58	1	$1,327,126.87	0	$0.00
Foreclosure	0	$0.00	5	$2,876,744.40	1	$94,738.61

*** To use this chart, locate along the Current Value row the desired delinquency status as of the immediately preceding due date (e.g. Current, 1 Month delinquent, etc.). Use the left hand column labeled Prior Value to see the prior month's value. Follow the selected Current Value column to the desired Prior Value row.

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Credit Enhancement
Type	Original Balance	Beginning Balance	Reduction	Increase	Ending Balance
Interest Coverage Account	$7,006,524.29	$0.00	$0.00	$0.00	$0.00
Over Collateralization	$0.00	$0.00	$0.00	$0.00	$0.00
Reserve Account	$0.00	$0.00	$0.00	$0.00	$0.00
Other	$0.00	$0.00	$0.00	$0.00	$0.00

Insurance
Insurance Type	Original Balance	Claims Paid	Coverage Remaining
Pool Insurance	$0.00	$0.00	$0.00
Other	$0.00	$0.00	$0.00

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Subordinate Class Certificate Balances
The Class Principal Balances of each Class of the Class B1,B2,B3,B4,B5,B6,B7,B8,B9,B10 Certificates immediately after the principal and interest distribution on 10/25/2007 are as follows:
Class	Ending Principal Balance	Percentage of Aggregate Certificate Principal Balance on Closing Date	Percentage of Aggregate Certificate Ending Principal Balance
B1	$32,460,381.62	2.00%	2.05%
B2	$36,516,682.00	2.25%	2.30%
B3	$12,172,892.58	0.75%	0.77%
B4	$52,745,874.93	3.25%	3.33%
B5	$19,476,228.97	1.20%	1.23%
B6	$8,114,596.47	0.50%	0.51%
B7	$7,303,336.40	0.45%	0.46%
B8	$5,680,816.25	0.35%	0.36%
B9	$5,679,818.38	0.35%	0.36%
B10	$14,607,599.93	0.90%	0.92%
Total	$194,758,227.53	12.00%	12.29%

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Glossary of Terms
TERM	DEFINITION
Average Ending Scheduled Principal Balance	Average scheduled principal balance of all mortgage loans as of the immediately preceding due date.
Compensating Interest	Interest paid by the servicer or master servicer in respect of Prepayment Interest Shortfall, subject to specified caps.
CPR (Constant Prepayment Rate)	The annualized, compounded single month mortality rate.
Current Interest Accrued	The interest accrued for the current month's distribution.
Deferred Interest	When a scheduled monthly payment is less than required to satisfy the note rate, the unpaid interest is deferred by adding it to the loan balance and the certificate balances.
Excess Liquidation Proceeds	Funds received at the time of liquidation in excess of the amount needed to satisfy the outstanding scheduled principal balance and related expenses.
Interest Rate Accrued	The rate at which interest is accrued for the current month's distribution.
Interest Rate Paid	The rate at which interest is paid for the current month's distribution.
Uncollected Interest	Interest not collected on delinquent loans for which scheduled payments are no longer being advanced, interest uncollected on prepayments and interest uncollected on liquidations.
Other Interest Shortfall	Any interest shortfall other than Uncompensated Interest Shortfall, Deferred Interest or Interest Uncollected on Non-Earning Assets.
Over Collateralization	Any excess of the aggregate principal balance of the mortgage loans over the aggregate principal balance of the certificates.
Prefunding Amount	The amount of cash being held for future loan purchases.

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Glossary of Terms (Continued)
TERM	DEFINITION
Prepayment Interest Shortfall	Any shortfall in collections of interest on mortgage loans resulting from prepayments in full or partial prepayments.
Principal Loss	The amount of principal reduction due to a loss realized on the mortgage loans.
Principal Reimbursed	The amount of principal passed through as a reimbursement.
PSA (Prepayment Speed Assumption)	A prepayment model that in its base case (stated as 100% PSA), assumes that prepayments start in month one at an annual CPR of 0.2%, rising linearly to 6.0% CPR in month 30, and then remain flat at 6.0% CPR thereafter.
Relief Act Shortfall	Interest shortfall resulting from application of the Servicemembers Civil Relief Act.
REO (Real Estate Owned)	Property acquired by the trust through foreclosure or deed-in-lieu of foreclosure on a defaulted loan.
Reserve Account	Funded or non-funded accounts set up at either the property or portfolio level in in anticipation of periodic or non-periodic capital expenditures or cash needs.
Servicer Advances	Scheduled principal and interest advances made by the servicer or master servicer for delinquent mortgage loans.
Servicing Fees	The monthly fee paid to the servicer to perform primary servicing function for the master servicer with respect to the mortgage loans and if applicable the fee charged by the master servicer for supervising the mortgage loan servicing.
SMM (Single Month Mortality)	In any given month, the SMM measures the percentage of the beginning pool balance that was paid back earlier than scheduled through payoffs.
Stop Advance	The amount of principal and interest on delinquent mortgage loans for which scheduled payments are no longer being advanced.
Subsequent Recoveries	The amount of funds recovered on mortgage loans that were previously liquidated at a loss.
Trigger Event	An event that may require a change in payment priority.

Series: WAMU 2007-OA4	Washington Mutual
Issue Date: 04/26/2007
Record Date: 09/28/2007
Distribution Date: 10/25/2007

Glossary of Terms (Continued)
TERM	DEFINITION
Unscheduled Interest	Interested collected in addition to the scheduled interest payment.
Unscheduled Principal	Payments of principal which were received with respect to any mortgage loan during the prior period, other than monthly scheduled principal, prepayments in full, repurchases, liquidation principal and subsequent recoveries.
Weighted Average Loan Age	For any distribution date, the weighted average of the loan age on the mortgage loans as of the immediately preceding due date.
Weighted Average Mortgage Interest Rate	For any distribution date, the weighted average of the mortgage interest rates on the mortgage loans as of the second preceding due date (after giving effect to the payments due on the mortgage loans on that due date).
Weighted Average Pass Through Rate	For any distribution date, the weighted average of the pass-through rates on the mortgage loans as of the second preceding due date (after giving effect to the payments due on the mortgage loans on that due date).
Weighted Average Remaining Term	For any distribution date, the weighted average of the maturity on the mortgage loans as of the immediately preceding due date.
MBA Delinquency Calculation	In this calculation, a loan increases its delinquency status if a monthly payment is not received by the end of the day immediately preceding the loan's next due date.
OTS Delinquency Calculation	In this calculation, a loan increases its delinquency status if a monthly payment is not received by the loan's due date in the following month.

WaMu Mortgage Pass-Through Certificates, Series 2007-OA4 10-D