Smart connected on 6-of-12 shots and distributed three assists for the Cowboys (17-5, 7-3 Big 12), who won for the sixth time in their last seven games.
Markel Brown supplied 17 points and Le'Bryan Nash contributed 14 with nine rebounds for Oklahoma State.
Ioannis Papapetrou finished with 15 points, seven rebounds and four assists, and Demarcus Holland scored 13 for the Longhorns (10-13, 2-8), who have lost eight of their last 10.
Members of Congress to keep receiving porn magazine
Putin thinks Obama would save him if he were drowning