Suisham booted one field goal in each of the first three quarters -- from 21, 28 and 23 yards. His last kick turned out to be the game-winner.
Quarterback Jason Campbell was 23-of-35 passing for 242 yards for the Redskins (1-1).
Clinton Portis rushed for 79 yards for Washington.
Marc Bulger completed 15-of-28 passes for 123 yards and a touchdown for the Rams (0-2).
Laurent Robinson caught the scoring pass on a 2-yard play and Steven Jackson ran for 104 yards for St. Louis.