The Eagles led by three points midway through the third quarter, but built that lead to a game-high 16 points late in the fourth.
Sophia Wiard had a big night for Oakridge with 15 points, 10 rebounds, five steals and five assists. Hannah Reinhold scored a game-high 16 points.
Montague, which finished the season 10-11, was led by Grace Meacham with 10 points and 11 rebounds.
Oakridge will take on Spring Lake at Montague High School on Friday night at 7 p.m. for the district crown.