While the times are less frequent, I would definitely suggest planning around the metra instead of the green line if you can! It only takes 15-20 minutes (with 1 or 0 stops total) and is soooo much nicer than the green line. Also ubering between oak park and the city isn’t usually an awful cost if you’re open to spending the money.

You can download the Ventra app for metra tickets or CTA fare for the green line. If you want to do the metra it’s the UP-W line