"This is very gratifying to play so well from the beginning, especially against a quality team like the Giants that is fighting for something," Redskins linebacker Brian Orakpo said. "They know us and we know them; we have a great book on them."
The loss knocked the Giants (7-7) out of first place in the NFC East. Dallas (8-6) now leads the division by a game with two to go, including one with Giants on the final weekend.
If New York beats the Jets and the Cowboys in its final two games it will win the division. The Cowboys play the Eagles next weekend and might wrap up the division if the Giants fall in their rivalry game with the Jets.
This loss was the fifth in six games for the Giants, who are now in danger of missing the playoffs for the third straight year.
"I'm very disappointed in how we played today," Giants coach Tom Coughlin said. "I accept responsibility for it. But I expected to see more - quality execution - and we didn't get that."
The scenario has been the same each season. New York starts the season quickly and then falters down the stretch, playing some unbelievably bad games with the postseason on the line.
This season it has been another collapse after a stunning win over New England left them at 6-2. They lost four in a row and then last week seemed to grab command again by rallying in the fourth quarter to beat the Cowboys in Dallas.
Again, with the playoffs in their grasp, they came out flat against the Redskins, who had already been eliminated from playoff contention.
Even a couple of gift interceptions by Grossman in the first quarter didn't help.
Gano gave Washington the lead on its second series with a 36-yard field goal that was set up in part by a 19-yard pass from Donte' Stallworth on a third and 12 from the Giants 39.
Grossman, who finished 15 of 24 for 185 yards, pushed the lead to 10-0 early in the second quarter with his TD pass to a wide-open Moss on third and 8.
If the touchdown had the fans muttering, there was no hiding their feelings minutes later after Oshiomogho Atogwe intercepted a pass that deflected off the hands of running back D.J. Ware and returned it 26 yards to the Giants 41. Nine plays later, Young scored and the fans let the team know it was sick of being let down.