Preheat oven to 450°F (230°C Gas Mark 8). Blend OLD BAY seasoning onion powder and dill weed. Set aside. Sprinkle seasoning mixture evenly over fillets.
Place fillet skin side down in baking pan coated with cooking spray; lightly brush surface with vegetable oil.
Bake 8-10 minutes per 2.5 cm of thickness or until fish flakes easily with a fork.