Miami (12-0, 7-0 Big East) extended the nation's longest winning streak to 34 games and secured a date in the national championship game against second-ranked Ohio State.
The national title will be decided in the Fiesta Bowl on Jan. 3 and the Hurricanes will try to become the first school to win back-to-back national championships since Nebraska in 1994 and 1995.
"We are extremely happy to be going to the Fiesta Bowl," Miami Coach Larry Coker said. "I am proud of our players, coaches and our 18 seniors. I am the luckiest football coach in the world."
A loss by the Hurricanes would have thrown the Bowl Championship Series into chaos. Instead, the oft-maligned system has resulted in a matchup of the only two undefeated teams in Division I-A.
The race for the Heisman Trophy is far less clear, but McGahee made a serious case for the sport's top individual honor. He broke the school's single-game scoring record of five touchdowns set by Bill L'ltalien against Piedmont in 1933.
"The offensive line did a great job. Coach Chud (offensive coordinator Rob Chudzinski) had a great game plan," McGahee said. "I was just hoping to score. I am satisfied as long as we keep moving the sticks."
McGahee's 39 carries tied a school mark set by Edgerrin James in 1998.
"My vote is for McGahee and he should not bother to hang around here anymore," Virginia Tech Coach Frank Beamer said.
Even if McGahee fails to win the award, he almost certainly secured an invitation to next Saturday's Heisman Trophy ceremony in New York City.
McGahee scored on runs of one, four, three, 10, one and 31 yards as Miami answered every threat by the Hokies (9-4, 3-4), who have lost four of their last five games.
"I'm proud of our players' efforts today," Beamer said. "We hung in there and made some big plays, but we missed some tackles and gave up long plays."
The 56 points were the most allowed by the Hokies since a 60-0 loss to Washington & Lee in 1951.
Quarterback Ken Dorsey made his own case for the Heisman Trophy, completing 12 of 20 passes for 300 yards and two touchdowns and improving his record as a starter to 38-1.
McGahee scored on runs of one and three yards in the first five minutes of the third quarter as the Hurricanes built a 49-21 lead.
Hokies backup Grant Noel had thrown a touchdown pass in the final 24 seconds of the first half to cut the lead to 35-21. But the Hurricanes came out firing after the break with Dorsey hooking up on a 68-yard pass to Andre Johnson, leading to a short touchdown run by McGahee.
Johnson caught six passes for 193 yards and score.
Virginia Tech was able to stay within striking distance with the help of Miami mistakes. Running back Jarrett Payton threw a pass on a trick play that was intercepted and returned 97 yards for a score by Willie Pile midway through the third quarter.
"We let them stay in the game too long. We were able to overcome our mistakes," Dorsey said. "It feels good to go undefeated and earn our way to play for a national championship."
A 20-yard field goal by Carter Warley and a nine-yard touchdown run by Lee Suggs, which came after Dorsey was intercepted, cut the deficit to 49-37 after three quarters.
Dorsey put away the game early in the fourth quarter with an 11-yard pass to tight end Kellen Winslow that made it 56-37.
Suggs had a four-yard touchdown run with 1:51 left, his third of the day, to cap the scoring.
The Hurricanes clinched their eighth Big East Conference title and won their 24th straight conference game. Miami also won its 22nd consecutive home game, the best streak in the country.
Miami rolled up 556 yards and improved to 24-0 under Coker, but the second-year coach might have reason to be concerned about his defense. The Hurricanes allowed their highest point total since a 66-13 loss to Syracuse in 1998.
The Hurricanes started quickly as Roscoe Parrish returned a punt 43 yards to the Hokies' 21-yard line. Dorsey found Johnson over the middle for a 23-yard gain on Miami's first play from scrimmage and McGahee soon scored on a one-yard run.
Bryan Randall fumbled near midfield on the Hokies' next possession and Dorsey capitalized by finding Johnson along the left sideline for a 49-yard touchdown pass to make it 14-0.
Virginia Tech answered on a one-yard touchdown run by Suggs early in the second quarter to cut the lead to seven points, but Miami struck right back.
Dorsey hooked up with Johnson on a 31-yard gain and a pass interference call put the Hurricanes inside the Hokies' five, setting up a four-yard touchdown run by McGahee with 9:57 left in the second quarter.
Kevin Jones fumbled on the Hokies' next possession and McGahee went in from three yards three minutes later, increasing the lead to 28-7.
Richard Jefferson kept the Hokies in the game with a 90-yard kickoff return, leading to a four-yard touchdown pass from Randall to Shawn Witten.
But any time it got close, Miami quickly boosted its cushion. Dorsey perfectly led Parrish with a pass up the sideline for a 58-yard gain and McGahee soon went in from 10 yards, increasing the lead to 35-14.
The Hokies cut the lead to 35-21 at halftime on a seven-yard pass from Noel to Ernest Wolford. Noel briefly replaced Randall after he was hit hard by linebacker Jonathan Vilma.