Trailing 23-21, Tulsa (5-3, 3-2 Conference USA) stopped SMU (1-7, 0-4) on fourth-and-goal at the Tulsa 1 with 1:56 left. With one time-out left, the Golden Hurricane went 99 yards in nine plays to score the winning touchdown.
Smith completed 27 of 45 passes for 336 yards and three touchdowns to lead Tulsa, which entered the game ranked third in total offense in the Football Bowl Subdivision (formerly NCAA Division I-A). It was the eighth consecutive game in which Smith passed for more than 300 yards.
Tulsa finished with 438 yards of offense but trailed most of the game because the Golden Hurricane committed five turnovers, compared to one for Southern Methodist.
Tulsa freshman receiver Trae Johnson caught 11 passes for 158 yards, both career highs, and a touchdown, while Clay had five catches for 106 yards.
Justin Willis passed for 192 yards and rushed for 44 yards to lead the Mustangs.
SMU, ahead 20-14 early in the fourth quarter, failed on a fourth-and-two play from the Tulsa 32 when a deep pass fell incomplete. Tulsa took advantage, as Johnson caught a 30-yard touchdown pass from Smith on the next possession to give the Golden Hurricane a 21-20 lead.
Thomas Morstead's 52-yard field goal with 10:42 left put the Mustangs back ahead at 23-21.
SMU opened up the scoring on an 18-yard second-quarter touchdown pass from Willis to Columbus Givens. Tulsa tied the game on its next possession on a 7-yard touchdown run up the middle by Smith.
Morstead kicked field goals of 50 and 32 yards, the latter on the final play of the first half, to give the Mustangs a 13-7 lead.
SMU went up 20-7 on their opening possession of the second half, as Emmanuel Sanders caught a 24-yard touchdown pass to put the Mustangs up 20-7.
But Tulsa answered with a 7-yard touchdown pass from Smith to Cameron Clemons to narrow the margin to 20-14.