The Green Knights (25-1-4), who have a 27-game unbeaten streak (23-0-4), advance to next weekend's Division III Final Four in Lake Placid, N.Y.
Tyler Chestnut stopped 35 of 37 shots in the season-ending loss for the Tommies (20-7-2). Nick Pernula scored 22 seconds into the second period (assisted by Andrew Panchenko) to erase a 1-0 SNC lead.
UST was outshot 37-22, including 14-5 in the last poeriod and overtime. The Toms were playing their second game in four days while the Green Knights were coming off a seven-day break. UST killed off alll three power-play tries by the winners.