The Longhorns (23-3, 11-0) have a two-game lead over No. 1 Kansas with five games left in the regular season.
Jordan Hamilton added 15 points and Tristan Thompson scored 14 for Texas, which has won 10 of the last 11 meetings with Oklahoma State (16-9, 4-7). The Longhorns have seldom been challenged in conference play, winning 10 of their 11 league games by 10 or more points.
Markel Brown scored 14 points to lead Oklahoma State.
The Texas winning streak has followed a typical pattern: The Longhorns race to a big early lead and then set the game on cruise control in the second half.
Texas hasn't trailed in a game since the first half of a 15-point win over Oklahoma State on Jan. 26, a span of seven games.
Hamilton scored 15 in the first half against the Cowboys on Wednesday night, hitting his first three 3-point shots before his shooting touch mostly disappeared. Thompson blocked Oklahoma State's first shot of the game to start another stellar defensive effort by the Longhorns. Texas forced the Cowboys into 12 first-half turnovers.
Thompson had an alley-oop dunk on a feed from Hamilton to start a 13-4 Texas run and the Longhorns built the lead as high as 33-19 when Hamilton made a short jumper in the lane. For the fifth straight game, Texas held a double-digit lead, 36-25, at halftime.
Texas has sometimes struggled to keep up the pressure in the opening minutes of the second half and let opponents rally. Not this time.
Johnson didn't allow it, dominating the first 7 minutes by scoring 11 of Texas' first 15 points of the second half. In one three-basket sequence, he stepped out for a long fadeaway jumper, posted up Oklahoma State's Roger Franklin for a three-point play, then got an easy tip-in after Hamilton's miss to put Texas up 51-34.
Cory Joseph then put the game away with about 12 minutes left. Joseph swished a 3-pointer when left all alone in the right corner, then finished a fast break with a layup off his own steal to put Texas ahead 56-35.
Texas shot just 44 percent and continued to struggle from the free throw line (16 of 28), but defensively held the Cowboys to 38 percent shooting. Texas has allowed an opponent to shoot better than 40 percent just once during the winning streak.