The Sooners (9-2, 7-1 Big 12) forced a 45-45 tie and overtime when Blake Bell capped a 17-play, 86-yard drive with a 4-yard scoring run with 4 seconds left in regulation.
The Cowboys got a 26-yard field goal from Quinn Sharp in the first possession of overtime, but then and Clay secured the win when he shed a pair of tacklers on his 18-yard scoring scamper on the Sooners' first OT try.
Landry Jones went 46-of-71 through the air for 500 yards, three TDs and an interception as Oklahoma kept its hopes of a Big 12 title alive with the victory in the 107th meeting of the intrastate rivals in their Bedlam Series.
Clint Chelf completed 19-of-37 passes for 253 yards, a TD and an interception, and Joseph Randle gained 113 yards with four scores on 21 carries for the Cowboys (7-4, 5-3).
Swim Week Miami Beach 2014 [PHOTOS]