Smart, who also had nine rebounds, scored on a pair of layups and a 3-pointer during an 11-4 Cowboy run in the second half that put the game out of reach at 54-35 with under eight minutes to play. Markel Brown had 13 points for Oklahoma State (3-0).
Trae Golden finished with 11 points for Tennessee (2-1).
Oklahoma State will face No. 6 North Carolina State in the championship game while Tennessee takes on UMass.