Place the oil in a deep pot or dutch oven and heat to 365-370°F.
Rinse and pat dry the cod fillets. Season lightly with salt and black pepper on all sides. Set aside.
In a shallow bowl, whisk together flour, cornstarch, baking powder, seafood seasoning, seasoned salt, paprika, garlic and onion powders. Remove ⅓ cup to a separate shallow dish.
Whisk egg and beer into remaining dry ingredients until fully combined to form batter.
Dip the coated cod fillet first into the reserved dry ingredients then into the batter allowing any excess to drip off. Carefully lower into the oil.
Cook in batches for 6-8 minutes total, turning as needed until deep golden brown. Have nearby a pan lined with paper towels to drain. Season lightly with additional seasoned salt immediately upon removing from oil.
Serve immediately with chips, malt vinegar or tarter sauce.