LUBBOCK, Texas -- Texas Tech coach Mark Adams was just happy fans stuck around for the biggest comeback in school history and the first Big 12 win of the season for a team that reached the Sweet 16 a year ago.

The Red Raiders erased a 23-point deficit after halftime to end an eight-game conference skid, with De'Vion Harmon scoring all 16 of his points after the break in an 80-77 overtime victory against No. 13 Iowa State on Monday night.

"I'm still in shock here," Adams said. "I was just so proud of our guys. They didn't give up on themselves. I was proud of the fans. I was afraid they were going to leave at halftime."

The Cyclones took a 59-36 lead with 12:38 remaining in regulation. At that point, they had a 99.6% win probability. However, Texas Tech tied the largest comeback by any team in Division I men's basketball this season, as well as tying the largest comeback to beat an AP-ranked team over the past decade and setting a record for the largest second-half deficit overcome to win a game in the history of the Big 12/Big 8.

One of Caleb Grill's career-best eight 3-pointers gave Iowa State that 59-36 lead, but the Red Raiders started a 20-3 run not long after to make it close down the stretch.

Kevin Obanor had 24 points and 13 rebounds for the Red Raiders (12-10, 1-8 Big 12), who won their second consecutive game, including a victory over LSU in the SEC/Big 12 Challenge.

Grill scored 24 points but missed his final three 3-pointers after starting 8-of-9. One miss was an off-balance air ball on a frantic game-ending sequence in which the Cyclones (15-6, 6-3) missed three from long range trying to force a second overtime.

"They just decided they were going to crank up the pressure, really come after us and try to spread us out," said Iowa State coach T.J. Otzelberger, whose team was coming off a double-digit loss to Missouri in the SEC/Big 12 Challenge that followed a win over fifth-ranked Kansas State. "We got out of sorts."

Iowa State's only field goal in the final 10 minutes of regulation was the 3-pointer that gave Grill his career high of eight. The Cyclones were 3-of-16 in the final 10 minutes of regulation and OT.

"This isn't a time to figure out who's fault it was and doom and gloom," Otzelberger said. "We've had some really great moments. We're going to continue to have some great moments."

Iowa State still led by five with 40 seconds remaining in regulation when Obanor hit a 3-pointer and the Red Raiders forced one of 13 second-half turnovers from the Cyclones on the inbound play.

Harmon, who had 11 points in the second half and five in OT, was fouled on a drive and made both free throws for the first tie of the game at 71-all with 21 seconds remaining after Iowa State had led from the opening bucket.

Iowa State's Gabe Kalscheur had 19 points but went 0-of-6 from 3, with one of the misses coming up short at the buzzer in regulation.

The Red Raiders took their first lead early in overtime on a layup by D'Maurian Williams, and their biggest lead was the final margin.

Harmon put them ahead for good with one of two free throws with 42 seconds remaining in overtime, and Obanor hit two more after another of Grill's late misses on an off-balance 3.

Grill had the first long try in the final seconds, and Jaren Holmes got the rebound but also was short from beyond the arc. Holmes ended up with the ball one more time but was short again as the buzzer sounded.

Texas Tech's biggest previous comeback was from 17 down in a 99-94 overtime victory at Nevada on Dec. 27, 1997.

"I thought our defense was much better [in the second half], but the big thing was just we were the most aggressive team on both ends of the floor the second half," Adams said. "That was the difference."

The Cyclones, who beat Texas Tech by 34 points at home last month, led by 17 at halftime -- their largest lead in a road conference game over the past 10 seasons -- and took their first 20-point lead on one of Grill's 3s in the opening seconds of the second half.

The Red Raiders rallied without freshman point guard Pop Isaacs, their leading scorer in conference play. He missed a second consecutive game because of an ankle injury, while 6-foot-11 senior center Fardaws Aimaq was out because of a foot injury.

The Associated Press contributed to this report.