The Horned Frogs (17-11, 4-11 Big 12), in their third season in the league, completed their first regular-season series sweep of a Big 12 opponent.
Williams scored six points in the first 4 1/2 minutes of the game to push TCU to an 8-2 lead. The Horned Frogs never trailed, and the game was tied only once -- for less than two minutes at 8-8, before Trey Zeigler had a steal that turned into a breakaway dunk.
Kyan Anderson had 17 points and six assists for the Horned Frogs. Zeigler finished with 15 points and Amric Fields had 10 off the bench.
Zach Smith and Keenan Evans each had 10 points for the Red Raiders (12-17, 2-14), who lost their sixth game in a row.
TCU won 62-42 in Lubbock on Jan. 17, still the only Big 12 road win for the Frogs since joining the league.
The Horned Frogs lost all 18 Big 12 games a season ago, after a 2-16 conference debut in 2013 with wins over Kansas and Oklahoma. After consecutive home wins over then-No. 21 Oklahoma State (70-55) and Kansas State (69-55), TCU lost 81-72 at No. 8 Kansas on Saturday.
TCU is playing its home games off campus this season in Wilkerson-Greines Activity Center, the arena used by the Fort Worth Independent School District. Daniel Meyer Coliseum on the TCU campus is undergoing a $59 million total renovation.
Texas Tech: The Red Raiders had 10 turnovers in the first half that led to 10 TCU points. They had three turnovers in an 86-second span, including two shot-clock violations.
TCU: It was the second career double-double for Williams, who had eight offensive and eight defensive rebounds.
Texas Tech is home Saturday against Oklahoma St.
TCU at No. 16 Oklahoma on Saturday.