Clinton Portis rushed for 108 yards on 27 attempts and one score. Portis also threw a touchdown pass, and Chris Cooley had five receptions for 41 yards and one touchdown for the Redskins (9-6), who have built a four-game winning streak and can clinch a playoff spot with a win at Philadelphia next Sunday.
The Redskins lost starting quarterback Mark Brunell to a sprained knee in the third quarter.
Eli Manning was 23-of-41 passing for 244 yards, one touchdown and one interception, Amani Toomer recorded six receptions for 85 yards and a touchdown while Tiki Barber gained 80 yards on 16 carries for the Giants (10-5), who still can win the NFC East with a win at Oakland.
Barber had a string of five straight 100-yard rushing games snapped.