The win puts Lawrence (14-3, 9-2 MWC) two games ahead in the conference standings with five games to play. Ripon (13-5, 7-4) is now tied for second with Knox.
The game was the first between the teams when both were ranked in the top 25. Lawrence and Ripon have been playing basketball since 1905.
MacGillis, whose previous career high was 22 earlier this season vs. Knox, hit on 8 of 12 shots from the floor and handed out a game-high five assists.
Jason Holinbeck and Dan Evans had 14 points apiece for Lawrence, and Brendan Falls and Chris Braier had 12 points apiece. Braier also had a game-high 14 rebounds despite not playing the final nine-plus minutes of the first half after picking up his second foul.
Tom Becker was outstanding for Ripon, as he scored 26 points on 11 of 23 shooting from the floor. Bo Johnson added 14 and Jered Massen had 10.
Lawrence took command early in the second half. Lawrence, which had led by as many as 12 points in the first half before Ripon trimmed that edge to 43-41 at the break, went on a 10-0 run.
MacGillis scored four points in that run and Holinbeck and Evans both hit 3-pointers to give Lawrence a 57-45 lead with 11:44 left.
The Vikings built the advantage to as many as 14 points, but Ripon crept back into the game again. Becker's layup with 1:57 left cut the lead to 71-64, but Lawrence hit 10 of 12 free throws in the final 1:34 to seal the victory.
Lawrence enjoyed a big advantage at the foul line, hitting on 24 of 29 attempts. Ripon was 7 of 12 from the line.
Lawrence is back in action Friday as it travels to Knox. The Vikings then play at Illinois College on Saturday.