Marist's score was the lowest ever in a MAAC tournament game, dating to 1982. The previous low was 37 points by Loyola (Md.) against Manhattan in 1993.
The top-seeded Stags (24-6) never trailed as they earned a semifinal berth against No. 4 seed Saint Peter's on Sunday.
Fairfield led 27-14 at halftime, and the closest the Red Foxes (6-27) got in the second half was nine points, 32-23, with 12 minutes left. The Stags then reeled off the next 11 points to put the game out of reach.
Needham also had six steals for Fairfield, which had 19 overall and enjoyed a 41-28 rebounding advantage.
Anell Alexis led Marist with 11 points and eight rebounds.