Cleveland State took permanent control with a 12-0 run in which Illinois-Chicago went scoreless for 5:53. Lee's 3-pointer ignited the surge, and Devon Long added five points.
Long's three-point play with 13:58 remaining gave the Vikings a 46-28 lead, and the Flames got no closer than seven points the rest of the way.
Mason was 8 of 12 from the field and added six rebounds. Lee finished with 10 assists.
The Big 12/SEC Challenge will again feature Kansas and Kentucky, this time at Rupp Arena. That's not the only exciting matchup in next season's midseason conference showdown.
Northwestern has never made the NCAA tournament, but the Wildcats' upward trajectory suggests 2016-17 could finally be the season it happens.
Dillon Brooks, who led Oregon with 16.7 points per game last season, and Tyler Dorsey will opt out of the NBA draft process and return to the Ducks, sources told ESPN.