Peel and slice onions into ½ inch rings. Separate rings and place in a dish.
Pour milk over onions. Cover and refrigerate 1-2 hours. Stir onions at least once during resting time.
Batter
Add flour and salt to a mixing bowl. Stir together.
Mix in beer.
Cover and let sit at room temperature for at least one hour.
Assembly and Cooking
Preheat oil to 375 degrees. Amount of oil used depends on size of pan. You want 2-3 inches of oil in pan.
Place flour into a bag.
Pour off milk from onion rings.
Place 3-5 onion rings in bag. Shake lightly so they are coated.
Place each onion ring into batter one at a time. Remove from batter with tongs or a fork, tapping tongs lightly on side of bowl to remove excess batter.
Place in oil.
Do not overcrowd pan.
Cook for 2-3 minutes per side until golden brown.
Remove from oil and place on a baking sheet lined with a baking rack.
Place baking sheet in a 175 degree oven to keep warm while cooking remaining onion rings.