1. Pour oil into deep fryer, large heavy skillet or saucepan, filling no more than 1/3 full. Heat oil to 375°F on medium heat.
2. Stir Batter Mix and beer or water in medium bowl until mixed. Dip onion rings into batter, one at a time. Carefully add onion rings, several at a time, to hot oil.
3. Fry 3 to 5 minutes, turning once to brown evenly, until onions rings are golden brown. Drain on paper towels.