The Yellow Jackets answered with a 20-yard field goal, but JD Falslev's third long kickoff return of the game put BYU back in business.
The Cougars promptly went 43 yards in three plays, capped by Riley Nelson's 39-yard shovel pass to Williams for the 17-year-old freshman's fourth TD. Justin Sorensen, who missed a chip-shot field goal earlier in the half, made the PAT to give BYU a 38-17 lead with 14 minutes, 50 seconds remaining in the game.
Sorensen added a 26-yarder midway through the fourth quarter to make it 41-17 for BYU.
The Cougars got off to a fantastic start, driving 55 yards for a touchdown on their opening possession. Williams picked it up on a 6-yard run.
BYU stopped Tech's spread option on its first possession, but the Cougars gave back the early touchdown after being pinned deep. Nelson's third-down pass was intercepted by Isaiah Johnson and returned 22 yards for a touchdown to pull the Yellow Jackets even.
After an exchange of punts, the Cougars put together a 58-yard touchdown drive to regain the lead. Nelson's 43-yard pass to Ross Apo set up Williams' 1-yard TD run on the first play of the second quarter.
Georgia Tech's Justin Moore missed a 35-yard field goal attempt with 10:27 remaining in the second quarter.
After Kyle Van Noy blocked a punt, the Cougars took over at the Tech 13 and hit pay dirt just two plays later. Nelson's tackle-breaking 10-yard TD run made it 21-7 with 4:46 remaining in the first half.
However, Georgia Tech's Jamal Golden returned the ensuing kickoff 97 yards for a touchdown, the Jacket's first kick return for a TD since 1998.
The Cougars drove to the Tech 6-yard-line just before halftime, but Nelson lost three yards on a sweep then threw a pair of incomplete passes. Sorensen's 26-yard field goal gave BYU a 24-14 lead at the half.