West completed 21 of 24 passes - setting a school record of 313.5 for passing efficiency - with Cooper Kupp hauling in 12 for 201 yards and three touchdowns.
Despite racking up 667 yards, the Eagles (1-2) didn't secure the win until Nzuzi Webster intercepted Dakota Prukop near midfield with nine seconds remaining in the nonconference battle between the two Big Sky Conference favorites.
Prukop threw for 353 and four touchdowns, and rushed for 196 yards and a score as Montana State (1-1) piled up 718 yards. The Bobcats ran 104 plays, picked up 40 first downs to Eastern Washington's 18 and had the ball for 15 more minutes. But the Eagles averaged 11.7 yards on 57 plays, recovered two onside kicks and stopped a pair of 2-point PAT attempts.
AP College Football website: www.collegefootball.ap.org