DePaul (26-7) made 16 3-pointers, one shy of a tournament record. Each Blue Demon starter finished in double-scoring after three quarters. Coleman led with 25 points as the Blue Demons built a 35-point lead, 83-48, and avenged last season's eight-point loss in the title game to the Golden Eagles in Milwaukee.
The teams tied for the regular-season title and split their two meetings, each winning on its home court. DePaul has won 12 of their last 13 games since their 26-point loss at Villanova on Jan. 19. Marquette (23-9) had its eight-game win streak snapped.
It is DePaul's third Big East Tournament title.
Seven DePaul players made at least one 3-pointer, four had five or more assists, and two finished with double-doubles.
Coleman made five 3s and was 9-of-13 shooting overall. Chante Stonewall added 14 points and 11 rebounds, and Kelly Campbell chipped in 10 points and 11 rebounds. Ashton Millender had 16 points and Mart'e Grays 14.
Amani Wilborn, last season's conference tournament Most Outstanding Player, scored 12 points before fouling out early in the fourth quarter for Marquette. Natisha Hiedeman added 10 points.
DePaul built a 22-17 lead in the first quarter and cruised with 30 and 31 points in the second and third quarters.
The Blue Demons were 38-of-74 (51.4 percent) shooting overall, and 16 of 35 (46 percent) from long range. They outrebounded Marquette 52-34 and finished with 27 assists. Lauren Prochaska led with eight assists and chipped in four points. Grays added six assists and Coleman and Campbell dished five apiece.
The Blue Demons, who lead the country in 3-pointers per game and second in 3-point attempts, shot nearly 40 percent (44 of 112) from long range in the tournament.
It was DePaul coach Doug Bruno's 1,000th game with the Blue Demons.