The Wildcats battled and got the win in three sets (25-22, 25-20, 25-14).
Laura Borras led the way with nine digs, eight kills and three aces, while Anastasia Trevino had 10 kills and three blocks.
Alissa Wynn added 20 digs with four aces and Jordan Netcott threw in 10 digs and an ace.
Montague (23-24-1) will be back at Fruitport on Thursday for the semi-final round. The Wildcats are set to match up with Orchard View.