McCown had a career night while making a fourth straight start for the injured Jay Cutler, completing 27-of-36 passes for 348 yards without an interception.
Forte racked up 175 total yards (102 rushing, 73 receiving) as Chicago broke a two-game losing streak and matched Detroit atop the division standings.
The Lions, however, hold the tiebreaker with two wins over Chicago.
The Cowboys (7-6) got three touchdown passes from Tony Romo but it wasn't enough to extend their two-game winning streak. They fell one game behind NFC East-leading Philadelphia.
Romo completed 11-for-20 passes for 104 yards without a turnover.