How To Reheat A Casserole

So glad you’ve come by! Let’s talk about how to reheat a casserole.

A casserole is an easy dish to make and doesn’t require too many steps.

It also comprises many great ingredients like cheese, meat, sauces, and pasta (or potatoes or rice), which ultimately makes it a family favorite. 

If you’ve ever made a casserole and had some leftovers, you’re not alone!

It’s quite possible to reheat leftover casserole—and still make sure it tastes good. 

If you’re trying to figure out how to reheat a casserole without drying it out or overcooking it, you’re in luck! 

There are a few easy ways to heat a casserole and let it retain its original taste as well.

Here’s what you need to know. 

Reheating casserole 

The trick to reheating anything is to take a step back and start by looking at it in reverse.

Has the whole pan or a serving that you now want to eat already been reheated?

If so, the quality, taste, and texture of most foods starts to deteriorate if you reheat foods more than once.

So if you have a large portion in the pan, start by dividing it into individual servings when you reheat your casserole.

Cut squares or plate servings that you know everyone will eat, and just start with heating those through, instead of reheating the entire pan off the bat.

You can reheat from thawed or from frozen (the majority of frozen foods we buy in the store have already been cooked then flash frozen, so we are all “reheating” those family-sized lasagnas and such. I guess they are technically starting out as leftovers by the time they come to us!).

I’ve found that pasta casseroles seem to fare much better with a better taste and texture when cooked from a frozen state instead of being thawed first.

1. Heating a casserole in the oven

If you want to reheat a leftover casserole in the oven, keep in mind that your aim is to warm it up, not bake it from scratch.

The ingredients have already been cooked, so you are heating it through.

• If you have a little casserole left (around two servings), you can warm it in the oven after it has been preheated at 400 to 425 degrees Fahrenheit. Cover it with tinfoil to keep it moist and leave it in the oven for around 10 to 15 minutes at most.
• If you have a slightly larger amount of casserole left, you can put it in the oven for about 20 minutes at most, at 350 degrees Fahrenheit. Remember to keep it covered with foil so that the casserole can retain its moisture and doesn’t dry out. You can use these temperatures and times for both meat-based and vegetable casseroles.
• This is where a meat thermometer is super useful. Instead of wrestling it out of the oven and guessing, use a thermometer to check whether the temperature towards the casserole’s centre is around 165 degrees Fahrenheit. If not, you can place it in the oven for a maximum of five minutes more but be careful not to let the edges burn.
• Using the oven is the best way to reheat a whole casserole.
• To reheat a whole pan of frozen casserole, make sure it’s tightly covered and heat at 400F for one hour for a 9×13 casserole that’s about two inches thick. The denser it is, the more time it takes; the looser it is, the less time it takes. If it has a cheese top that you want to brown, remove the lid/foil at the 45-minute mark. 

There’s also the fact that when food sits out for too long past the defrosted stage, it starts to encourage bacterial growth. So to be safe, cook your whole or half-pans of casseroles from frozen. and don’t defrost them first.

2. Reheating a casserole in the microwave

Like reheating a casserole in the oven, you’ll need a microwave-safe dish to reheat a casserole in the microwave.

• Heat it for around two to five minutes at high heat if your microwave doesn’t have an automatic reheating option. Keep it at two if you have fewer servings, and aim for five if you have a larger portion leftover. Keep checking the temperature and ensuring the casserole isn’t drying out or losing its shape from excessive heat.
• When heating the casserole in the microwave, never use tinfoil. A microwave-safe lid like this one, another plate, a paper plate or a paper towel, are all good options for keeping in heat and moisture while reheating food in the microwave.
• Most people prefer reheating leftover servings of a casserole in the microwave because it’s faster and doesn’t require preheating.

How to defrost a frozen casserole 

Like I mentioned above, defrosting a frozen casserole before reheating is not always ideal.

But if you must defrost a whole or half-pan of frozen casserole before reheating it thoroughly:

• If it’s a microwave-safe dish, use the defrost setting on your microwave.
• If it’s NOT in a microwave-safe dish, defrost overnight, covered, in the refrigerator.

I used to leave out my frozen lunches on my desk so that I didn’t have to wait so long when I was ready to microwave them. (See my note above about how most frozen lunches are “leftovers” by the time they get to us.)

For some meals, it was fine, they reheated in the break room microwave okay, but here is my list of frozen meals that I thawed to room temp or close to room temp before microwaving them and the results:

• All frozen lunches (think Marie Callender’s, Healthy Choice, etc.) with potatoes bigger than 1/2 inch. The potatoes tasted watery and the texture was very mealy and loose.
• Breakfast sandwiches and breakfast bowls: Something bad happens to the sausage that has been cooked, frozen, thawed, then reheated. No bueno. The egg too, but not as bad as the sausage.
• While it didn’t taste terrible, most of the pastas come out much better if cooked from frozen instead of thawed. If the pasta was cooked past al dente either at home or the manufacturer, the texture when thawed is gummy or pasty.
• Corn tortillas, so enchilada meals and the like, disintegrated into mush when it defrosted and the heat just helped it along that journey into unpleasant goo. If you have a Mexican casserole that you want to reheat, cook it from frozen, for sure.

There’s also the fact that when food sits out for too long past the defrosted stage, it starts to encourage bacterial growth. So to be safe, cook your whole or half-pans of casseroles from frozen. and don’t defrost them first.

Tips from the pros

• If you’re worried about the heat not thoroughly distributing throughout the casserole when you’re warming it up, you can also cut it into smaller pieces or serving sizes to allow heat to reach the innermost parts of the casserole. You can also move it into a more appropriately sized, oven-friendly dish.
• When you’re storing leftover casserole in the refrigerator, be sure to consume it within two days. Leaving it in the fridge for longer will cause the casserole to go bad. If you’ve kept it in the freezer, don’t freeze it again after taking it out. Instead, it’s better to finish it within a day of defrosting it.
• When your casserole has a topping such as breadcrumbs or crackers, you will want to set it in the oven for a minute or two without tinfoil so that topping can become crispy again—even if you’ve heated it in the microwave. This is just an added measure if you want to recover some of the topping’s original crispiness but be careful that you don’t burn it.
• Always make sure your casserole reaches an internal temperature of 165 degrees Fahrenheit to ensure that it’s safe to eat.
• If you’re heating your casserole in the oven, rotate the dish every few minutes to allow an equal amount of time in each position so that the casserole heats more evenly.
• People often like to use one trick to prevent the casserole from drying out in the oven – that is placing an oven-safe dish of water in the oven, creating a kind of “sauna” for your casserole. You might need to transfer the casserole to a bigger dish for this step. It would also help if you then covered the whole thing with tin foil again. This comes in handy when you have pasta, noodles, or vegetables in your casserole and are afraid that they’ll dry out. 

The bottom line

Hopefully, you now have a clearer idea of how to reheat a casserole, whether whole or just a few leftover servings. 

Remember to keep checking that it reheats thoroughly and keep an eye on it for burned edges or the signs of drying out.

If you’re vigilant, you’ll have a great reheated casserole that’s ready to serve in no time.

Remember, foods reheated more than one time lose their optimum flavor and texture, so if you anticipate having leftovers from your reheated casserole, divide into individual servings before freezing.