Pour oil into deep fryer or a large, heavy bottom pot, filling no more than 1/3 full. Heat to 185-190°C on medium heat.
Lightly sprinkle fish with OLD BAY. Mix flour and 4 teaspoons of OLD BAY in a medium bowl. Stir in egg and gradually add beer, stirring with a wire whisk until smooth.
Dip fish into batter and shake off excess before adding to hot oil.
Fry fish, a few pieces at a time for 3-5 minutes or until golden brown, turning once for even browning. Drain onto paper towels.