A microwave may be ideal when you're desperately hungry and you only have cold leftovers available, but many dishes will be more appealing if you reheat them in a conventional oven. Reheating food in an oven takes longer, but it's worth the wait if you have the patience and you want to thoroughly enjoy your food even if you're enjoying it the second time around. It will also save you the stress and sparks from accidentally putting food wrapped in aluminum foil in the microwave.
To reheat leftovers in an oven, use relatively low heat and cover dishes that should stay moist.
Reheating Leftovers in the Oven: Fried Food
Fried food is ideal for oven reheating because its delicate crispiness depends on cooking out the moisture. Onion rings or fried chicken will get soggy when you store it in the refrigerator, but the dry heat of an oven is a great antidote for this sad state. The trick to reheating fried leftovers is to heat them until they're hot throughout and they have regained their crispiness, but no longer than that. Use less time for foods such as French fries that are fried in smaller pieces, and use additional time for bigger items such as fillets of fried fish.
Preheat your oven to 325 or 350 degrees Fahrenheit. The lower temperature will be more forgiving, especially for fried foods that come in smaller pieces, but it will take longer for you to get your food hot enough to be appealing. The higher temperature will heat your food more quickly, but you'll need to pay closer attention to identify the sweet spot between perfect and overdone.
Reheating Leftovers in the Oven: Casseroles
Because casseroles are baked in the oven the first time around, it makes perfect sense to reheat them that way as well. The long, slow cooking softens ingredients and melds flavors during the original cooking and during the reheating process as well. As with reheating fried foods in a conventional oven, it makes sense to use low heat so the temperature can diffuse evenly through the dish without burning the outside while the middle is still cold. It can take 30 to 45 minutes to reheat a casserole in the oven.
When reheating a casserole in the oven, it's especially important to cover your pan to keep the food from drying out. You can use aluminum foil if your casserole pan doesn't have a fitted lid, but make sure the foil isn't touching the food, especially if your casserole has cheese or tomato on top. Aluminum foil reacts with tomato, and melted cheese will stick to the foil, and you'll lose some of the best part of the dish.
A metal stem thermometer is a useful tool for determining whether the casserole is fully cooked in the middle. Poke it into the center of the casserole because that is the part that will heat most slowly. Check until it reaches an internal temperature of 165 degrees Fahrenheit. You can also use a remote oven thermometer, which consists of a probe and a remote temperature reader. This device will save you from having to continually open the oven door, and you can even set it to beep when the casserole reaches the right temperature.
Reheating Leftovers in the Oven: Stews
A Dutch oven is a heavy pan usually used for stews. It is designed for stove-top cooking and also for dishes that simmer slowly in the oven, like pot roast. Just as you can do your initial round of Dutch oven cooking in the oven, you can also use this pan for reheating your stew.
Like a casserole, a stew in a Dutch oven can take at least 30 minutes to cook. Unlike a casserole, you can stir a stew while it's reheating to lessen the risk of burning or uneven heating.