Do I need to preheat the oven for all types of cooking?

No, preheating is recommended for optimal results when baking cookies, breads, cakes, pies, or pastries, but there is no need for preheating when roasting meat or baking casseroles. For broiling, preheating is suggested when searing rare steaks by setting controls to BROIL for 3-4 minutes or until the element turns red-hot.