South Carolina -- which trailed, 28-27, at the half -- out-scored Houston, 14-8, in a pivotal fourth quarter.
Mitchell completed 19-of-29 passes for 323 yards. Cory Boyd scored twice and picked up 94 yards on 18 carries.
Kevin Kolb passed for three touchdowns and 386 yards for Houston. Jackie Battle scored twice and gained 85 yards on 11 carries, while Mark Hafner caught a TD pass and Vincent Marshall caught two scoring passes for the Cougars (10-4), who had a six-game winning steak snapped.
Marshall caught nine passes for 201 yards.
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