After BYU scored on their first drive of the game, their offence couldn't string together any momentum at all the rest of the way as the Texas Tech defence dominated.
They forced four total turnovers in the second half alone, with two fumbles and two interceptions, converting them to a total of 20 of their final 34 points.
Texas Tech's Ben Roberts became the first player in Big 12 Championship history with multiple interceptions.
Every 12 of Texas Tech's wins this season were by 20 points or more - a program record.
Full game recap + highlights
After Texas Tech failed to score on their first drive for just the fourth time this season, BYU made sure to respond in the best way possible.
Wide receiver Chase Robert eclipsed 2,500 career receiving yards, also making it 38 straight games with a reception, before they found paydirt.
Cougars running back LJ Martin capped off their 14-play, 90-yard drive with his 12th rushing touchdown of the season to go up 7-0.
Much like Robert, Martin would surpass 2,500 career rushing yards later in the game.
It was the first time all year that Texas Tech allowed points on the opening drive.
After going down 7-0, it also became just the third time all season that Texas Tech found themselves trailing in a game - it wouldn't last for long.
BYU would be held to just 24 yards the entire rest of the first half, totaling 114 yards (77 passing, 37 rushing).
The Red Raiders went down the field in their second drive on 11 plays for 70 yards, but came away with a 23-yard field goal from Stone Harrington to start the second quarter to make it 7-3.
Texas Tech would then force BYU to go three-and-out for the first time in the game, regaining possession with 13:30 left in the second quarter, which ultimately led to another score.
Behren Morton completed a 33-yard touchdown pass to Coy Eakin down the sidelines to put Texas Tech up 10-7 with what ended up becoming the highlight of the game.
BYU failed to gain any momentum in the first half at that point, being forced to punt on two of their next three drives, the other being a failed fake-punt pass attempt.
The Red Raiders' Harrington would miss a 48-yard field goal wide left as the BYU defence came in the clutch following Jack Kelly's 10th sack of the season. But Harrington would make up for the previous mistakes.
Harrington drilled a 40-yard field goal to put Texas Tech up 13-7 heading into halftime, scoring on three of their last four drives of the half.
The Red Raiders totaled 228 yards (142 passing, 86 rushing) in the first half.
2nd half
BYU ended their first drive of the second half with a 46-yard missed field goal from Will Ferrin.
They'd force a clutch turnover on downs on a 4th and 2 within their own 20 after Texas Tech tried for the endzone, forcing an incompletion.
BYU's offence would fail yet again as QB Bachmeier threw his fifth interception of the season.
After Texas Tech's Ben Roberts forced the clutch takeaway, running back Cameron Dickey found the endzone untouched one play later to go up 21-7 (converted a two-point conversion).
It would mark Dickey's 14th rushing touchdown of the season. He finished the game with 72 yards on 18 attempts, with 20 receiving yards on four receptions.
Another BYU drive saw yet another turnover.
Texas Tech's A.J. Holmes Jr. would knock the ball loose on a Bachmeier run that eventually led to yet another Harrington field goal to give the Red Raiders a commanding 24-7 lead with 13:00 left to go in the fourth quarter.
It was Holmes' first forced fumble of the season. He finished the championship with three tackles, one sack, one tackle for loss, and a forced fumble.
Roberts would commit his second interception of the game on the very first play of BYU's drive, shutting down all hope of a BYU comeback.
Their defence would force a BYU turnover on downs before eventually finding the endzone for the final time in the game, thanks to a second Morton-Eakin connection for a 28-yard touchdown to put them up 31-7.
Then, just like they'd been doing all second half, Texas Tech's John Curry forced yet another turnover with a fumble on BYU's next drive.
It led to yet another Texas Tech score with a 28-yard field goal from Harrington, ending with the final 34-7 score.
BYU's season officially came to an end on Saturday after their loss in the Big 12 Championship, making it their last hope to secure a spot in the College Football Playoffs.
Texas Tech's Morton finished the game with 215 passing yards and two passing touchdowns on 20-of-33 passing.
Running back J'Koby Williams led all backs with 80 rushing yards on 15 carries. Reggie Virgil led all receivers with 86 yards on eight receptions.