Cut fish into 3-inch strips. Sprinkle evenly with 1 tsp. Greek seasoning, 1 tsp. salt, and 1/2 tsp. pepper.
Combine flour, cornmeal, baking powder, remaining 1 tsp. Greek seasoning, 1/2 tsp. salt, and 1/2 tsp. pepper; stir well. Add 2 cups cold beer and egg, stirring until thoroughly blended and smooth.
Pour oil to a depth of 2-3 inches into a Dutch oven (or large skillet/electric skillet); heat to 375.
Dip fish strips into batter, coating both sides well; shake off excess. Fry fish, in batches, 2 minutes on each side or until golden brown. Drain on paper towels.