Mike Shanahan shifted back to Grossman after John Beck's three straight starts resulted in losses and an anemic offense.
The new quarterback didn't lead to a new result, however, as the Redskins lost 20-9 to the Dolphins for Miami's first win at home since Nov. 14, 2010.
Shanahan said he decided to go with the more experienced quarterback because of a wave of injuries to the Redskins' offense.
"I thought Rex gave us a chance to win," Shanahan said after the game. "If you have this many guys go down, I didn't want to go with the inexperienced guy and throw him to the wolves."
Grossman threw for 215 yards and two interceptions in the Washington loss.
"I have to be more careful in a crucial point in the game," Grossman said of his miscues.
The Redskins began the season 3-1 with Grossman as the starting quarterback but he was benched in favor of Beck after throwing four interceptions in a loss to the Philadelphia Eagles on Oct. 16.
Beck, however, has thrown four interceptions to just two touchdowns in his three starts as the Redskins are now 3-6 after Sunday's road defeat.
Information from The Associated Press was used in this report.