After a typical slow start, Washington faced a 10-3 first-quarter deficit, but after a 10-0 third quarter, the Lions faded.
Moss compiled 220 all-purpose yards by sprinting 80 yards for a touchdown on a third-quarter punt return and catching nine passes for 140 yard, including one scoring reception.
Washington quarterback Jason Campbell completed 23-of-28 passes for 328 yards, one touchdown and no interceptions. Clinton Portis gained 126 yards on 24 carries in the Redskins' third win in their last four games.
Detroit quarterback Dan Orlovsky went 21-for-35 for 223 yards, one touchdown and no interceptions.
Calvin Johnson scored once on four catches for 57 yards.
Shaun McDonald caught five passes for 68 yards, but Detroit gained only 57 yards on 15 rushing attempts.
The Lions (0-7) have lost eight straight dating back to last season.