Forte's 32-yard scoring run midway through the first quarter opened the scoring and gave Chicago a lead it wouldn't relinquish.
Jay Cutler completed 17-of-32 pass attempts for 226 yards, overcoming a pair of interceptions while hooking up with Roy Williams on a 25-yard scoring strike in the second quarter.
Williams and Johnny Knox combined for seven catches for 112 yards as the Bears (4-3) took their second straight victory after routing Minnesota 39-10 last week.
Josh Freeman rallied the Buccaneers (4-3) with a pair of fourth-quarter scoring strikes to Kellen Winslow and Dezmon Briscoe but couldn't erase Tampa Bay's 16-point deficit.
Freeman finished with a 29-of-51 passing efficiency for 264 yards but was intercepted four times in the loss.