How to Reheat Onion Rings. As with any deep-fried food, onion rings are ideally are consumed just after they're made, but you can still reheat them to a credible state. While many restaurants recommend using a deep fryer to reheat onion rings, here is a way to do it without.
Things You'll Need
Leftover Onions Rings
Preheat oven to 350 degrees F.
Wrap leftover onion rings in aluminum foil.
Place onion rings in oven for 3-5 minutes (or until crispy).