Scott Bamforth had 15 points and Kyle Tresnak 14 for the Wildcats (21-4, 13-1 Big Sky), who moved a half-game in front of idle Montana for first place in the conference standings. Weber State, which defeated the Grizzlies in January, visits Montana in the regular-season finale on Feb. 28.
Shawn Reid scored 31 points and made five 3-pointers for the Bobcats (11-14, 6-8), and Mohammed Fall added 13 points.
Montana State played its first game since leading scorer Xavier Blount suffered a likely season-ending shoulder injury and broken nose when assaulted outside a Bozeman bar early Sunday morning. MSU linebacker Roger Trammell was charged with misdemeanor assault and dismissed from the football team.
The 20-year-old Blount, who was averaging 11.7 points a game, was charged with disorderly conduct and minor in possession of alcohol. Two other MSU athletes were cited for various misdemeanors.
Lillard had four steals for the Wildcats, who never trailed and shot 54.2 percent (26 of 48) from the floor for the game.
Montana State used a 22-6 run to start the second half to get within 48-46. But Jordan Richardson hit a 3-pointer to ignite a 10-0 Weber State run, and the Bobcats got no closer than six points the rest of the way.