Stevenett's heroics at the end capped a comeback which saw the Thunderbirds erase an 11-point deficit in the final 2:50 after trailing 81-70.
Reggie Hamilton, who led all scorers in the game with 31 points, missed two free throws with 1:28 to go before Ray Jones, Jr., hit a basket and free throw with 1:16 to play pulling SUU within 81-79.
Hamilton was fouled again, this time hitting the second of two free throws for an 82-79 Golden Grizzly lead. That set the stage for a three-point basket by SUU's Damon Heuir, which tied the game at 82 with 1:09 left.
OU missed a three-point shot and SUU got the ball out of bounds, setting the table for Stevenett's basket.
OU missed another field goal attempt, and Stevenett was fouled with 2.6 seconds left but missed both free throw attempts. OU's last try, by Drew Valentine, also missed the mark allowing the sixth-seed SUU to advance to Monday's semi-final game against South Dakota State.
Southern Utah jumped off to a 21-10 lead in the first nine minutes, with Stevenett scoring eight points. Oakland came back and tied it at 26 on a three-pointer by Hamilton, who scored 11 straight OU points over a two minute stretch which saw the Golden Grizzlies take a 34-32 lead.
But SUU wouldn't go away, coming right back to open a 40-35 lead on a layup by Ramell Taylor and two free throws by Heuir with 17 seconds left put the Thunderbirds ahead 43-40 at intermission.
SUU made 16-of-24 field goal attempts in the second half, and finished the game shooting 58 percent (32-for-55). Stevenett, a 6-4 junior, hit 10-of-16 field goal attempts and led SUU with 26 points while Heuir was 8-for-13 and finished with 23. Reserve Wade Collie went 5-for-5 from the field en route to 14 points.
Oakland shot 51 percent and counted 15 three-point baskets among its 26 field goals (26-for-51). Hamilton was 10-for-18 including 6-of-8 on three-point attempts. Travis Bader added 23 points and Valentine had 11 rebounds as the Golden Grizzlies won the battle of the boards 28-27. Oakland ends its season 17-14.
Men's Printable Bracket