SALT LAKE CITY -- Brian Johnson threw for 303 yards and four touchdowns, and his favorite play was the one that went nowhere.
The Utah quarterback took the snap, dropped to his knee and then let the mayhem begin as the eighth-ranked Utes beat No. 16 BYU 48-24 on Saturday, completing a perfect regular season and securing another trip to the Bowl Championship Series.
"Couldn't ask for a more fitting end," Johnson said as he made his way through the swarm of red-clad fans who were still on the field long after the game ended.
There was plenty to celebrate.
Utah (12-0, 8-0) won the rivalry for the first time in three years and took the undisputed Mountain West Conference title away from the two-time defending champion Cougars (10-2, 6-2).
Johnson completed 30 of 36 passes and had no turnovers for Utah, which blew the game open with three touchdowns in the fourth quarter.
"We took it as a challenge for our entire offense. All we heard about was how explosive BYU's offense was and how inconsistent we were throughout the entire year," Johnson said. "We wanted to show people that when we put it together we can be pretty good."
Utah forced six turnovers by BYU quarterback Max Hall, including a career-worst five interceptions, and ruined the Cougars' hopes of claiming a share of the conference title after winning the last two outright.
Hall's troubles snowballed in the second half as the Utes turned the turnovers into points and the celebration grew louder with every touchdown.
The last unbeaten Utah team was the BCS Busters of 2004, who were 11-0 before winning the Fiesta Bowl.
The Fiesta is one of the possible bowl destinations for the Utes, who were No. 7 in the BCS standings last week and now just have to wait for the announcement Dec. 7.
"We won't worry about anything we can't control. We are very pleased and feel very fortunate and blessed to be where we are right now," Utah coach Kyle Whittingham said.
Utah fans couldn't wait to celebrate and charged the field with 29 seconds left. They were herded off so Johnson could take a knee and run out the clock, then returned and the Utes were swallowed in the sea of red.
The chant "B-C-S!" rang out through Rice-Eccles Stadium as Johnson received the Mountain West title trophy.
While Johnson's night was nearly perfect, Hall's couldn't have gone much worse. He had thrown for 34 touchdowns this season, but ran for his only score on Saturday. Three of his interceptions led to scores for Utah, as did his fumble at the BYU 31 late in the third quarter.
"It was a fun game to play in. The crowd was way into it and it developed a lot of momentum for Utah. At times we were able to just play through it," Hall said. "Utah just played a great game tonight, give credit to them."
The Cougars pulled within three in the third quarter, then imploded in the fourth.
"Utah was opportunistic and made the most of those opportunities and we did not," BYU coach Bronco Mendenhall said. "That is as clear as I can put it."
Hall cut it to 27-24 on an 11-yard touchdown run with 6:46 left in the third and the Cougars' defense forced a punt to get the ball right back, but it didn't stay with BYU for long. Hall had the ball knocked from his hand when he tried to run as the pocket collapsed around him.
Paul Kruger recovered for Utah at the BYU 31 with 8 seconds left in the quarter and the Utes scored early in the fourth on Johnson's 8-yard touchdown pass to Brent Casteel.
On the next possession, Kruger dropped back from defensive end into pass coverage, plucked Hall's pass out of the air and started heading the other way. Hall tripped up Kruger to keep him from scoring, but it was at the 4 and Utah quickly scored on a pass from running back Matt Asiata to Chris Joppru for a 41-24 lead.
"We knew to win this game we'd have to have some big plays and then we had capitalize on those opportunities and we did," Kruger said.
Hall threw another interception to Sean Smith, who returned it 38 yards to the BYU 29. Johnson completed the short drive with a 4-yard touchdown pass to Colt Sampson with 2:48 left.
The Utes were the ones making the mistakes in the first half with two crucial penalties that allowed BYU to tie it after Utah had gone up 17-3.
Kruger was offsides on a play that would have been a sack by Koa Misi, so instead of fourth down with a long field-goal attempt BYU had third-and-1 from the 23. Harvey Unga took a pitch around the left end, made one cut inside and easily scored to cut it to 17-10.
Utah had BYU stopped at the 14, but Brice McCain was called for pass interference and the Cougars had first-and-goal from the 2. Unga scored on a direct snap with 6:26 left in the half.
Louie Sakoda kicked two field goals for the Utes.
The intensity of the rival was evident before the game started. The Cougars had just done their ritual "haka" war dance and Utes crossed over toward the other sideline for some words. Officials kept the confrontation to pointing and shouting and no players got close enough to each other to turn it physical.