For many summers now, the Austin Gardens Park near the corner of Lake Street and Forest Avenue in Oak Park has doubled as the nighttime performance venue for Oak Park Festival Theatre. The park is medium-size, with plenty of trees and grass, providing a soothing and pastoral setting for catching a bit of theater. The plays themselves are presented on a pretty basic wooden stage built for the occasion each summer, but it's the area in front of the stage that provides the real cushiness: Patrons are encouraged to arrive early and bring a picnic dinner. Bring a blanket to sit on the lawn, bring your own lawn chairs, or rent a chair at the park for two dollars.
Concessions, refreshments, T-shirts, posters and play scripts are also on sale for fairly reasonable prices. There are plenty of restaurants in the area; Lake Street is essentially the "downtown" of Oak Park, and parking is available in decks and at meters near the park. A little secret: If you park in the parking deck on Forest Avenue, you don't have to pay as long as you're leaving after it closes that night at 10 p.m.
As for the experience itself: The outdoor nature of the venue does have its down sides. Bring plenty of bug spray and be prepared for the possibility of rain. Occasionally airplanes or passing police or ambulance sirens can disturb audience enjoyment of the plays. It's pretty much a relaxed, laid-back way to spend a summer evening, especially if you bring a picnic basket or smuggle in a bottle of wine (technically against park rules).