Here is a little look at some MLB stadiums that hosted a college football game. In the same weekend, Northwestern and Illinois played at Wrigley, with Notre Dame and Army hooking up in the Bronx. As far as I can remember, those games are the only regular season games played in a converted stadium. 5 current MLB stadiums hosted a bowl game in the 2000s. Here are 4 of them, because Sun Life Stadium hosing a football game isn't that special, because they have one nearly every weekend.
Northwestern-Illinois @ Wrigley Field
Notre Dame-Army @ New Yankee Stadium
Beef O'Brady's Bowl @ Tropicana Field
Kraft Fight Hunger Bowl @ AT&T Stadium
Former International Bowl @ Rogers Centre
And finally, for one year in 2000, the Insight Bowl was played at Chase field.
I might do a post on the new Qatar Stadiums for you all! Comment, please.