Preheat the oven to 350 F. Slice the onion into large rings. In a shallow dish, combine egg and milk. In another dish, combine flour and seasoning. Place the breadcrumbs into the last dish.
Coat each onion ring into the egg mixture, then into the flour mixture, then back into the egg mixture, and then coat fully into the breadcrumbs.
Place the onion rings onto a large greased baking sheet. Bake for 20-25 minutes.