We did both in one day on the Saturday before Easter. It was hectic and probably not ideal but also we had less time between the tours. The Northwestern one was at 9:30 and I think was supposed to go to 11:15 and the U Chicago one was supposed to start at noon with an hour-long info session followed by a tour. @momzhood is right, parking for the Northwestern tour was one of the most convenient parking situations for a tour ever - and I’ve been on a lot of tours - in the parking lot right next to the beautiful visitor center. We knew that U Chicago parking would be harder and planned in advance to use the lot that they recommended that is about a 10-minute walk to the start of the tour. we left the Northwestern tour about 15 minutes early as we felt we’d gotten enough of an idea and we were about 5 minutes late for the start of the U Chicago info session. So leaving a good hour between is just barely enough time I’d say. But it is do-able and we lived to tell about it!