Stevenson 57, Rockford Boylan 41
Stevenson led by eight at the half and then held the Titans scoreless in the third quarter.
Lee scored 17, Dylan Richter added 13 and junior guard Kevin Stineman had 12 points.
Stephon Valentine had 10 for Boylan and UIC recruit Tori Boyd added seven points and seven rebounds.
Stevenson and O'Fallon will play in the first semifinal game tomorrow.