Don't Wait For The Oven To Preheat When Warming Casserole Leftovers

Casseroles are a godsend. Mix together any combination of protein, starch, and vegetables and you'll craft something delicious with ease. Not to mention that casseroles are a great meal to keep on hand when you just don't feel like cooking. Whether you've frozen a tray for a lazy day, or have a half-eaten casserole sitting in your fridge as we speak, knowing how to best reheat leftovers is a must. It's for this reason that we'd like to share that you don't need to preheat your oven when warming up leftover casserole. And, in fact, you shouldn't.

Forget everything you've been taught about preheating your oven, well, almost everything. Let's start at the beginning. Preheating consists of letting an appliance reach a set temperature before adding food to cook. The benefit of preheating is that certain raw foods need to be handled at specific temperatures in order to develop properly, like baked goods that must rise. Additionally, preheating ensures that foods like raw chicken reach a safe temperature within a given time. However, when it comes to leftovers that have already been cooked, preheating isn't necessary.

In the case of casseroles, leftovers should actually never be added to a preheated oven. The reason is simple: the cold casserole dish may crack. Despite being able to withstand extreme temperatures, vessels made from ceramic, glass, or enameled cast iron undergo thermal shock when they're pulled from a cold fridge (or freezer) and added directly to a hot oven — who knew?

Although you could wait for leftover casserole to reach room temperature before sticking it into a preheated oven, that could take a while. Instead, by forgoing the preheat, you can keep a casserole in its original baking dish (saving you from having to clean more dishes) without having to worry about destroying your cookware since temperatures rise gradually. But, before adding last night's casserole into a non-preheated oven, there are a few other guidelines you should follow.

To avoid compromising quality, start by covering the casserole dish with foil. This will better trap heat and work to keep things moist. You might also want to introduce extra moisture, whether by drizzling broth or dairy directly into the casserole or creating a bain-marie to prevent excessive drying. Of course, to maintain a golden and crisp exterior, we always recommend finishing the casserole uncovered.

As for what temperature to bake leftover casserole, that depends. Generally, baking at a lower temperature (between 300 and 350 degrees Fahrenheit) will promote even cooking. Casseroles can take half an hour to warm up, but it could be longer if reheating from frozen — note that skipping the preheat only adds mere minutes to overall cook time. To check that your casserole has reached an ideal internal temperature of 165 degrees Fahrenheit, don't hesitate to use a kitchen thermometer. For a perfectly warmed result, keep these tips in mind the next time you reheat a casserole!