Peel brown skin from onions and cut into 1/8" slices; chill overnight to make them easier to separate into rings. Reserve inner rings for something else. Prepare batter: Mix flour, baking powder, sugar, Lawry's Seasoning Salt, and garlic powder.
Stir in 1 can (11 ounces) beer until batter is consistency of cream. Dip onion rings in milk and then in flour to cover completely. Heat frying oil to 365 degrees. Dip onion rings in batter and cook them in oil for 10 seconds. Lift basket and separate rings, then cook in oil again till golden brown, about 3 minutes. Drain, discard any broken rings. Salt and serve immediately.