Bailey's 37-yarder proved to be decisive after Romo had completed 23-of-37 passes for 292 yards and three scores for Dallas (6-4), which logged its third consecutive win.
The Redskins (3-7) blew a 17-10 lead in the fourth quarter but forced overtime when Rex Grossman tossed a 4-yard TD in the final minute of regulation.
He finished with 289 yards and two touchdowns while Jabar Gaffney hauled down seven passes for 115 yards and a touchdown in the loss.
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