Larsen and McDonald each made five shots from the field while Lasan Kromah, who had led George Washington (3-3) in scoring the past two games, finished with 10 points on 4-of-6 shooting.
The game went back-and-forth, as neither team led by more than four. Charles Cooke broke the games' seventh tie with a free throw to put James Madison (1-5) up 48-47 with 3:12 left.
But the Dukes would not see the lead again, as Larsen hit a layup to help George Washington retake the lead, 52-48, and Patricio Garino hit a 3-pointer to put the Colonials ahead for good.
James Madison scored just one basket over the final two minutes before Andre Nation sank a desperation heave at the buzzer.
Cal big man Ivan Rabb could have been selected in the top 10 of the NBA draft. Instead, he's returning to Berkeley to make himself, and the Golden Bears, stronger.
Devin Williams' decision last month to sign with an agent and enter the NBA draft has left West Virginia in a tough spot.
Florida State's student government has passed a resolution discouraging Seminoles fans from wearing Native American headdresses at games.