The Bears trailed 19-14 after Buffalo's Corey McIntyre scored on a 1-yard TD run midway through the final quarter.
But Tim Jennings intercepted Ryan Fitzpatrick and returned it to the Bills' 23-yard line with 9:03 left in the game. Jay Cutler found Greg Olsen on an 18-yard pass to the 5-yard line and Bennett later caught Cutler's short toss for the go-ahead score.
The Bears' quarterback completed 17-of-30 passes for 188 yards and two touchdowns, also carrying the ball five times for 39 yards.
Fitzpatrick went 31-of-51 passing for 299 yards with a touchdown and two interceptions for the Bills (0-8). The team hasn't remained winless for so long since 1984, when they started 0-11 and finished with a 2-14 record.