Montana State's Beau Sandland caught 5 passes for 156 yards and two touchdowns.
The Bobcats held Cal Poly to five yards per play a week after allowing Eastern Washington nearly 12 yards per attempt.
Montana State (2-1, 1-0 Big Sky) took a 28-7 lead early in the second quarter, but Cal Poly whittled it down to 31-21 when Kori Garcia scored from six yards out with 23 seconds left in the first half.
Montana State kicked off to start the third quarter and scored touchdowns on consecutive drives to open a 45-21 lead. The Bobcats scored on their first seven possessions of the game.
Joe Protheroe ran for 156 and a TD to lead Cal Poly (1-3, 0-1 Big Sky).
AP College Football website: www.collegefootball.ap.org