Fish can easily be prepared in the oven by baking. Typical baking temperature is between 200 and 350 degrees Fahrenheit, while temperatures higher than this are used for roasting fish. Baking allows more flexible cooking times and is more suitable to prepare moist fish, according to the "Joy of Cooking." The time it takes to bake a fish until it is done depends on the size of the fillet, steak or whole fish as well as the baking temperature. You can figure out if fish is cooked with few simple techniques.
Calculate the baking time based on the thickness of the fish fillet or steak. "Joy of Cooking" says eight to nine minutes per inch of thickness works as a general guideline for baking fish. The actual baking time depends on the fish species, temperature and whether you are baking with liquids. Begin to check for doneness after six to seven minutes per inch.
Gently cut the fish with a knife to check the interior. When it is opaque throughout, the fish is done.
Poke the fish with a fork. Cooked fish flakes and is firmer than when fresh.
Insert an instant-read meat thermometer in the thickest part of the fish. All fish is cooked when it reaches 137 degrees Fahrenheit, according to "Joy of Cooking."