Tender, flaky and mild tasting, frozen halibut fillets are best cooked straight from the freezer without thawing first, making for an easy meal with minimal preparation. Because the thickness of frozen fillets varies, plan for 10 minutes of baking time per half inch of thickness, measuring the fillet at its thickest point. Add five minutes of baking time if you are wrapping the fish in foil or baking it in a sauce.
Preheat oven to 450 degrees. Grease an oven-safe baking dish or cookie sheet with melted butter or oil.
Remove your frozen fillet from its wrapper and rinse, removing any debris and patting dry with a paper towel. Place your fillet skin-side down on your greased baking dish. The U.S. Food and Drug Administration advises home cooks to wash both hands and utensils that come into contact with uncooked seafood before handling other ingredients.
Drizzle melted butter or oil over your fillet to keep it moist. Sprinkle seasonings such as salt, pepper and herbs over your fillet. To prevent your halibut from drying out, baste it with extra butter, oil or pan juices halfway through the baking time.
Bake your frozen fillet for 10 minutes per 1/2 inch of thickness until the fish has turned opaque or white. Use a food thermometer to test the internal temperature of the fillet, or slide a fork or thin knife into the thickest part of the fish, making sure it offers no resistance and flakes easily.
Remove the fillet from the baking pan using a wide spatula and spoon any pan juices over the fish. Serve with a squeeze of fresh lemon, if desired. Any skin left in the baking dish will lift and clean easily.