Hamline led by as many as 19 in the early moments of the second half. The Oles cut the Piper lead, which was a big as 19 in the second half, to 67-64 on on Chad Norberg's 3-pointer with 1:19 to play.
Norberg had a steal on the ensuing possession, but Mark Bergstrom's three-point try to tie in the corner missed.
Jon Butala had a team-high 21 and Jon Bain 16 points for St. Olaf (7-9, 4-7 MIAC) in the loss.
Foster had 14 points in the first half, including 12 on three-point tries (4-for-6). The Pipers, as a team, were 7-for-13 from the arc in the first.
The Pipers went on an 18-2 run in the closing minutes of the first half.
The loss was the Oles' fourth in MIAC play by six points or fewer and the third in a row by four or less. St. Olaf lost 60-57 to Gustavus on Monday and 68-65 to Macalester on Jan. 10.