Underwood was led by Mo Bugbee (17 points, 3 steals), Kallyn Grove (10 points, 4 rebounds, 3 steals), Liz Lukken (8 points, 5 steals, 5 assists), Mia Blaskowski (7 points, 8 rebounds, 3 assists) and Zoey Swanson (7 points).
Underwood (9-2) will travel to Hancock on Tuesday to face the defending Class A champions.
Brandon-Evansville (1-6) has a non-conference game at Henning on Saturday.