Bernard Berrian had three receptions for 79 yards and a touchdown and Cedric Benson rushed for just 33 yards on 19 attempts with one touchdown for the Bears, who improved to 3-0 in the preseason.

Chicago's Devin Hester left the game with a shoulder injury. He injured the shoulder blocking on a running play with about nine minutes left in the first quarter.

San Francisco starting quarterback Alex Smith went 4-of-8 with 47 yards before Trent Dilfer entered in the third. Dilfer completed 9-of-12 passes for 90 yards and two touchdowns for the 49ers, who fell to 1-2 in preseason play.

Grossman, who completed 13-of-20 pass attempts, led Chicago to a touchdown on the game's opening possession, a field goal on their second drive, and touchdowns on the third and fourth possessions.

Benson capped the first drive with a two-yard touchdown run less than 3 1/2 minutes into the game. Robbie Gould kicked a field goal of 37 yards with 7:14 left in the first quarter and Berrian caught a 25-yard touchdown pass five seconds into the second quarter to give the Bears a 17-0 lead.

Maurice Hicks put the 49ers on the board with a 2-yard touchdown run with 11:51 left in the half before Grossman capped a 11-play, 73-yard drive with a two-yard touchdown pass to Desmond Clark with 5:21 to play in the second quarter.

Walt Harris picked off a screen at the San Francisco 48 and ran it all the way into the end zone to trim the Bears lead to 24-13 with 3:13 left before the half. Adrian Peterson, though, extended Chicago's lead with 36 ticks to go in the frame with a two-yard touchdown run.

Dilfer connected with Zach Hilton on a three-yard touchdown pass five seconds into the fourth quarter and found Jason Hill for a nine-yard touchdown pass with 1:52 left to play.