Katie McGuire had 34 points to lead the Beavers. McGuire hit a 3-pointer with 33 seconds left in regulation to send the game to overtime, and hit one with 1:33 left in the extra session to tie the game 88-88.
Grimsrud finished with 15 points.
Christine Schwichtenberg and Christina Sampson had 18 points apiece to lead the Oles.
The Beavers' Kelli Staley had 20 points, including 17 in the first half, but fouled out with 7:20 remaining in regulation.
BVU led 44-36 at the break. St. Olaf went on a 23-8 run to start the second half and led by as many as nine in the frame.
Kristina Stoermer had all 16 of her points in the second half and overtime, going 8-of-11 from the field after the half.
Natalie Rigelman added 10 points in the win. The Beavers' Tracy Hartwig and Katie Ernst had 11 points each in the loss.
St. Olaf has now won all three meetings between the schools, each by three or less.
The Oles host Martin Luther College on Monday at 5:30 p.m.
STO 91, BVUW 88 BVUW (0-0) MAGUIRE, Katie 12-24 3-4 34; STALEY, Kelli 6-14 6-6 20; ERNST, Katie 3-7 5-6 11; HARTWIG, Tracy 3-15 4-4 11; GRIGGS, Jess 3-10 0-0 6; MEYER, Lindsey 1-6 1-1 3; HEITMANN, Penni 1-3 1-2 3; SCHWEITZBERGER, Jenn 0-3 0-0 0; DAVISON, Lynnsey 0-2 0-0 0; STOELK, Courtney 0-5 0-0 0. Totals 29-89 20-23 88. STO (0-2) Christina Sampson 6-11 2-3 18; Chri. Schwichtenberg 6-12 3-6 18; Kristina Stoermer 8-11 0-0 16; Holly Grimsrud 5-17 5-7 15; Natalie Rigelman 3-7 4-4 10; Britta Hendrickson 4-8 0-0 8; Laura Jorgensen 1-1 0-0 3; Mary Kleingarn 1-1 0-0 2; Danielle Stoermer 0-1 0-2 0. Totals 34-69 15-25 91. BVUW.......................... 44 34 10 - 88 STO........................... 36 42 13 - 91 3-point goals-BVUW 10-35 (MAGUIRE, Katie 7-16; STALEY, Kelli 2-4; HARTWIG, Tracy 1-6; MEYER, Lindsey 0-3; DAVISON, Lynnsey 0-1; STOELK, Courtney 0-2; GRIGGS, Jess 0-3), STO 8-19 (Christina Sampson 4-8; Chri. Schwichtenberg 3-5; Laura Jorgensen 1-1; Holly Grimsrud 0-4; Kristina Stoermer 0-1). Fouled out--BVUW-GRIGGS, Jess; STALEY, Kelli, STO-None. Rebounds-BVUW 46 (HEITMANN, Penni 12), STO 45 (Natalie Rigelman 10). Assists-BVUW 18 (MAGUIRE, Katie 8), STO 24 (Holly Grimsrud 7). Total fouls-BVUW 25, STO 25.