The Bears blew the game open with a 21-point second quarter, which gave them a 27-0 halftime advantage.
Grossman was 15-of-27 for 182 yards. Thomas Jones gained 109 yards on 22 carries, Bernard Berrian scored a touchdown on four receptions for 97 yards, Cedric Benson rushed for two scores and Rashied Davis also caught a touchdown pass for the unbeaten Bears (4-0), who are off to their best start since 1986.
J.P. Losman, who prevented a shutout with a 5-yard touchdown pass to Lee Evans late in the fourth quarter, completed just 14-of-27 passes for 115 yards. Willis McGahee ran for 50 yards on 14 carries and Evans made nine catches for 94 yards for the Bills (2-3).