Kareem Jamar had 11 points, seven rebounds and seven assists for the Grizzlies (13-4, 9-0), which moved into sole possession of first place in the Big Sky Conference after Weber State lost 79-74 at Montana State. Montana hosts Weber State on Saturday.
Neveij Walters led the Bengals (4-14, 3-6) with 12 points, and Melvin Morgan had 10. Idaho State shot 39 percent from the field, to Montana's 52 percent, and was outrebounded 31-20.
Idaho State led 31-29 at halftime, but Montana's 17-4 run to start the second half put the Grizzlies in control. The Bengals got no closer than nine the rest of the way.
Montana improved to 95-44 all-time against Idaho State and has won the last six meetings between the schools.