Yes, we have three versions of the Chicago Tribune on Online Resources A-Z.
Chicago Tribune Historical Archive contains searchable scanned images, which appear exactly like the printed copy of the Chicago Tribune, including classified and display advertisements, from 1849 to 1990.
Chicago Tribune (1985 to present) includes only the text of the articles in the Chicago Tribune (including the RedEye) from 1991 to present, but it is searchable. Some scanned images of articles may be included when the coverage in Chicago Tribune (1985 to present) overlaps the coverage in Chicago Tribune Historical Archive.
Finally, there’s the ProQuest Digital Microfilm. You can’t search this one—it’s just like using a microfilm reader. You can view page images of the Chicago Tribune and more than 80 other newspapers. Coverage for the Chicago Tribune begins in 2008 and ends about three months prior to the present. (Hint: If you are looking for the page image of an article dated after 2008, first search Chicago Tribune (1985 to present), locate the page number of the article, then find the page in ProQuest Digital Microfilm.)