The turkey is traditionally stuffed early in the morning and roasted for hours. Since it’s a long, slow cook, there’s no need to preheat your oven, even when the recipe suggests it.
This also holds true for a holiday ham. In fact, unless you’re baking breads or pastries, you may not need to preheat the oven at all. Don’t open the oven door to take a peek at what’s cooking inside. Instead, turn on the oven light and check the cooking status through the oven window.
Opening the oven door lowers the temperature inside—by as much as 25 degrees—which increases cooking time and wastes energy. As long as your oven is on, cook several items at the same time. Just make sure you leave enough room for the heat to circulate around each casserole and pie plate.
In an electric oven, you can turn the heat off several minutes before your food is fully cooked. As long as the oven door remains closed, enough heat will be stored inside to finish cooking your meal. The same principle applies to your electric range-top—the metal heating elements stay hot even after the electricity is turned off. If you use glass or ceramic pans, you can turn your oven temperature down 25 degrees, and foods will cook just as quickly.