Bergstrom had 11 of his team-best 14 in the second half. Jon Bain added 10 points and nine rebounds for the Oles (12-13, 9-11 MIAC) who, before Wednesday, hadn't won in St. Peter since Jan. 6, 1999.
Trevor Wittwer had 19 points, on 8-for-11 shooting, and eight rebounds for the Gusties (13-11, 11-8 MIAC) who led 23-9 with 8:11 to play in the first half and 30-21 at halftime.
St. Olaf charged back with a 14-5 run to tie the game at 41-41 and a 12-4 run in the final eight-plus minutes to seal the win.
St. Olaf, as the sixth seed, will play at third-seeded Bethel University at 7:30 p.m. on Monday.
ST. OLAF COLLEGE 58, GUSTAVUS ADOLPHUS COLLEGE 52 ST. OLAF COLLEGE (12-13 (9-11)) Mark Bergstrom 5-13 2-3 14; Jon Bain 3-4 4-5 10; Jon Butala 4-9 1-2 9; Brady McMahon 4-6 0-0 8; Mitch Haugen 2-10 3-4 7; Bobby Hunter 2-4 0-0 4; Chad Norberg 1-3 0-0 3; Mark Torell 1-2 0-0 2; Steve Banick 0-6 1-2 1. Totals 22-57 11-16 58. GUSTAVUS ADOLPHUS COLLEGE (13-11 (11-8)) Trevor Wittwer 8-11 2-2 19; Phil Sowden 6-13 1-1 13; Jay Stien 3-5 2-2 8; Kane Sivesind 2-7 0-0 5; Andrew Doble 2-3 0-0 4; Andrew Olson 1-4 1-2 3; Tyler Kaus 0-3 0-0 0; Mike DesLauriers 0-1 0-0 0; Tyler Kramer 0-1 0-0 0; Jesse Van Sickle 0-3 0-0 0. Totals 22-51 6-7 52. St. Olaf College.............. 21 37 - 58 Gustavus Adolphus College..... 30 22 - 52 3-point goals-St. Olaf College 3-5 (Mark Bergstrom 2-2; Chad Norberg 1-1; Jon Butala 0-1; Steve Banick 0-1), Gustavus Adolphus College 2-14 (Trevor Wittwer 1-2; Kane Sivesind 1-5; Andrew Olson 0-2; Tyler Kaus 0-2; Jesse Van Sickle 0-1; Phil Sowden 0-2). Fouled out--St. Olaf College-None, Gustavus Adolphus College-None. Rebounds-St. Olaf College 36 (Jon Bain 9), Gustavus Adolphus College 33 (Trevor Wittwer 8). Assists-St. Olaf College 9 (Jon Bain 3), Gustavus Adolphus College 10 (Tyler Kaus 3). Total fouls-St. Olaf College 9, Gustavus Adolphus College 17.