Gasser also grabbed eight rebounds and Jared Berggren contributed 12 points for the Badgers (23-8, 12-6 Big Ten), who won four out their final five Big Ten Conference games.
Ryan Evans chipped in with 10 for Wisconsin, which will go into this week's conference tourney with a first-round bye.
The Illini (17-14, 6-12) couldn't translate Brandon Paul's 22 points into a win, instead falling for the eighth time in nine contests.
Meyers Leonard grabbed 12 rebounds for Illinois, which has the ninth seed in post-season play.
Notable deaths of 2014 [PHOTOS]