Wambach, selected Most Valuable Player of Founders Cup III, netted both goals for the Freedom, which had fallen to Carolina in last year's championship.
Atlanta's Charmaine Hooper converted a penalty kick in first-half stoppage time to answer Wambach's first strike, but the Beat was unable to take advantage of its second-half dominance and lost a playoff heartbreaker for the third successive year.
The winner came moments after Beat defender Nancy Augustyniak -- the best player on the field -- was sent off for a last-man foul as Wambach raced toward the Atlanta net. Augustyniak dived in just above the box, and referee Terry Vaughn produced a red card. Mia Hamm's ensuing free kick from 19 yards struck the crossbar.
Less than two minutes later, in the 96th minute, another Washington counter finished off Atlanta. Jacqui Little found Meier on the right, and the German forward raced past Julie Augustyniak -- Nancy's twin -- and sent a cross to the far post, where Wambach and Hamm were free.
Wambach slid at the ball, striking it past Beat goalkeeper Briana Scurry with her left foot, and the celebration was on.
The Beat, which has gone to overtime in all five of its playoff games the past three seasons, fell to the then-Bay Area CyberRays on penalty kicks in the first Founders Cup. Last year Atlanta lost in the semifinals to Carolina after surrendering a lead on an 89th-minute penalty kick.
The game was played before an announced crowd of 7,106 -- the league said the game was sold out, although there were plenty of empty seats behind the west goal -- most of which favored Washington.
The Freedom, with Hamm causing havoc on the left and Wambach dominating in the middle, ruled most of the first half. Atlanta found little room to attack and struggled to possess the ball, enabling Washington to counter and create at will.
Wambach struck early with a trademark goal, a 12-yard header in the seventh minute that skipped past Scurry at the left post. The cross came from German defender Sandra Minnert, about 40 yards out on the left flank.
Hooper pulled Atlanta even in the first minute of stoppage time after Jacqui Little tripped up Leslie Gaston, who was cutting into the top of the Freedom box from the left wing. Little caught Gaston's trail foot, sending the rookie defender sprawling, and Vaughn pointed to the spot.
Hooper fired to the right as Mullinix, leaning the other way, stood and watched.
The goal took something out of Washington, and Atlanta took charge in the second half, dropping Homare Sawa deeper and bringing on Maribel Dominguez at halftime for Nikki Serlenga. The Beat finally managed some possession, although strong chances materialized only sporadically.
The Beat suffered from poor service, and Coach Tom Stone was forced to made three changes -- removing midfielder Marci Miller in the 65th, Cindy Parlow in the 89th and Gaston at the start of overtime -- because of exhaustion rather than tactical reasons. Both changes for Washington, with Meier coming on for Kelly Golebiowski in the 64th and Casey Zimny replacing Lindsay Stoecker in the 70th, worked wonderfully.
The Freedom outshot Atlanta, 11-3, in the first half and 20-9 for the match, but Scurry made two superb stops -- diving to stop a Wambach header in the 29th minute and leaping to poke away Minnert's exquisite 31-yard free kick to the upper-right corner -- and Augustyniak schooled Hamm repeatedly in one-on-one situations.
FOUNDERS CUP III
Aug. 24 at Torero Stadium, San Diego
Atlanta 1 Washington 2 (OT). Goals: Hooper pen. 46+; Wambach (Minnert, Moore) 7, Wambach (Meier, J. Little) 96.
Atlanta -- Scurry; Bivens, N. Augustyniak, Nonen, Gaston (J. Augustyniak, 91); Miller (Warren, 65), Serlenga (Dominguez, 46); Parlow (Withers, 89), Sawa; Hooper, Pohlers.
Washington -- Mullinix; S. Little, Moore, Grubb, Minnert; J. Little, Stoecker (Zimny, 70), Jones, Golebiowski (Meier, 64); Hamm; Wambach.
MVP -- Abby Wambach (Washington)
Yellow cards -- Atlanta: Bivens 29, Warren 71, Hooper 78; Washington: Wambach 58, Grubb 82. Red card -- Atlanta: N. Augustyniak 94.
Referee -- Terry Vaughn. Assistants -- Karalee Sutton, Dinesh Singh. Fourth official -- Jennifer Bennett.
A -- 7,106.
Previous Founders Cup results
2001 (at Foxboro, Mass.) -- Bay Area CyberRays 3 Atlanta Beat 3 (OT)
Bay Area wins title, 4-2, on penalty kicks
2002 (at Atlanta) -- Carolina Courage 3 Washington Freedom 2