Lee scored 20 of his points in the second half, when the Dragons (9-12, 5-4 Colonial Athletic Association) outscored the Patriots 33-16 en route to their fourth win in five games.
Drexel used a 9-0 run midway through the second half to take its first lead of the game, 50-49, with 7:17 remaining. The Patriots (12-9, 5-4) had only two field goals over the final 10:51.
Down 57-54 after Lee's 3-pointer, George Mason had opportunities but couldn't capitalize. Vertrail Vaughns stepped out of bounds, forcing the Patriots to foul. Then, after Drexel's Frantz Massenat missed the front end of a 1-and-1 at the other end, Jonathan Arledge was unable to secure the rebound, losing the ball out of bounds.
Lee missed the front end after being fouled on the ensuing inbounds, but recovered to poke the ball away from Bryon Allen and then hit 1 of 2 foul shots with 2 seconds remaining to seal the win.
Lee made 11 of 19 shots and also had nine rebounds and three steals. The sophomore's performance came just three days after he scored 30 points in a 66-64 loss at Delaware on Monday.
George Mason took command early, jumping out to a 12-1 lead as Drexel missed its first eight shots. Halfway through the first half, the Dragons had more turnovers (4) than points (3).
But after the Patriots extended their lead to 33-13 on a 3-pointer by Corey Edwards with 3:41 remaining, Drexel went on a 12-5 run, and Lee's 3 at the buzzer cut the deficit to 38-25 at halftime.
Sherrod Wright scored 15 points and Arledge added 14 points for George Mason. Arledge was starting in place of forward Johnny Williams, the team's second-leading scorer, who sat out after suffering a concussion in the Patriots' loss at Northeastern on Sunday.