Breunig was 9 of 15 from the field and Gregory finished on 5-of-11 shooting, including 4 of 7 from long range.
Montana (5-7, 2-0 Big Sky Conference) shot 26 of 47 for 55.3 percent from the field, and outrebounded North Dakota 33-20.
Montana built a 35-25 halftime lead, and the Grizzlies stretched their lead to 50-38 with 14:10 to go when Gregory hit back-to-back 3-pointers. Montana held a double-digit advantage until Quinton Hooker's jumper pulled North Dakota within 69-61 with 2:11 left. The Grizzlies shot 5 of 6 from the line to seal it.