Williams has now rushed for 1,202 yards this season, 2,016 for his career. That ranks him No. 10 on BYU's all-time career rushing yardage list.
Williams' 66-yard touchdown run on the second play of the second half broke BYU out of its offensive malaise.
"I really just have to get myself pissed off, to go out there and hit somebody and just keep doing it," he said. "Because they get tired of tackling if you keep running at them with so much force and aggression."
Quarterback Taysom Hill rushed 26 times for 154 yards and a touchdown. It was the fourth time this season that Hill and Williams have eclipsed the 100-yard plateau.
It is the first time in BYU history that two players have rushed for more than 1,000 yards in a season.
"Huge, huge, huge," BYU coach Bronco Mendenhall said of Williams' touchdown run. "It showed instant credibility and change from the message that was [delivered] at halftime. So that was giant."
Mendenhall said he and offensive coordinator Robert Anae decided to turn the game over to the offensive line and Williams and Hill's rushing ability toward the end of the first half.
"We knew that was the direction we were going to have to go, and so the combination of running the football with Jamaal and Taysom, and then the quick [throw] game, and moving the chains that way, that was the difference," Mendenhall said. "That approach helped us."
The Cougars finished with 394 rushing yards, the fifth game with 300 or more rushing yards this season. They are 5-0 in those games.
A closer look
BYU running back Jamaal Williams against Nevada:
Att Yds TD
First half 3 32 0
Att Yds TD
Second half 12 187 1