Bears coach Lovie Smith made the announcement on Wednesday and his choice of Grossman was apparently not based solely on Griese's sprained shoulder.
"We're going to go with who gives us the best opportunity to win," Smith said.
Grossman said he hopes to be the starter for the remainder of the season.
"I'm trying to keep this job for the rest of the season, I think that's a given. I've already been benched, what are they going to do to me? I've been there and I don't want to go back," Grossman said.
"I'm just excited about going out and playing football and not worrying about the repercussions of it."
Griese took over for the struggling Grossman after the third game this season, but sprained his left shoulder when he was hit late in the first half of the Bears' game against Oakland on Sunday.
Grossman relieved Griese and threw a 59-yard, go-ahead touchdown pass to Bernard Berrian with 3:11 to play as the Bears rallied for a 17-6 victory.
During practice on Wednesday at Halas Hall, Grossman took snaps with the first team, while Griese was in a baseball cap. Griese told reporters he hoped to practice Thursday and be able to play Sunday, but that's not the scenario Smith mapped out. Smith said both quarterbacks had been informed of the switch for Sunday's game.
Griese has completed 62 percent of his passes and has nine touchdown passes with 10 interceptions, including four in one game against Detroit. Chicago is 3-3 in games he has started.
Grossman has completed 52 percent with two touchdown passes and six interceptions. The Bears are 1-2 with him as a starter this season.
Copyright 2007 by The Associated Press