Can You Reheat Onions? – The Best Way

Onions are the delight of nearly any meal. Even if you don’t like to eat raw onions, you can’t help but want to cook with them. They add such a change in flavor that simply can’t be matched without the onion. 

You can use onions in almost any type of dish you make. From burgers to casseroles and everything in between, your dish is not complete without those onions. Many times, cooked onions are used as a topping for burgers and sandwiches and such. 

The thing is, you can’t really cut an onion open without cooking up the whole onion. So then you feel like you have to cook the entire onion. And that leads to tons of leftover cooked onions. 

Can you reheat your cooked onions? Yes, you can reheat onions on the stovetop or in the oven. Your success with reheating onions may vary depending on how they were originally cooked.

We’ve put together this simple guide to walk you through everything you might need to know about reheating onions. We will cover various details about onions, including proper storage of your cooked onions. 

Keep reading to learn all about reheating onions and more!

A Guide to Reheating Onions

Let’s start with the basics. You probably already know what an onion is. And no, we don’t mean the news source in this instance. The onion is a unique and versatile vegetable. It comes from the same family of things like shallots, leeks, garlic, and chives. 

You can find the onion in a number of variations. There are red, white, and yellow onions. Beyond that, you also get into sweet onions and so forth. Each of these does vary in taste and sometimes in what they are used for. 

There is no guide that says specifically when to use which onion. If you’re an onion connoisseur, you might have some knowledge here. You might even just have a specific preference that you normally cook with. 

No matter which type of onion you are using, they are versatile and can be used for many different things. When it comes to our guide to reheating onions, the instructions will be the same for each type of onion. 

Since the overall makeup of the onion is the same regardless of which style it is, the instructions do not vary based on the kind of onion. 

You might see some variance in instructions based on how the onion was cooked. For instance, fried onions and sautéed onions are not the same after cooking. Therefore, the reheating process might vary slightly. 

We will get to all of those details soon. 

Common Uses for Cooked Onions

As we mentioned before, onions are pretty versatile. You can use them in nearly everything you cook. Most things with onions simply have the onions cooked into them. However, there are dishes that you might cook the onions separately and then add them as you please. 

Maybe your family really likes to top your various meals with sautéed onions. That’s awesome! You can sauté a full onion at one time to cut down on your work. You just need a method for reheating them later. 

Here are some great ideas for using your cooked onions:

• Onion blossoms
• Top a hamburger
• Add to quesadillas
• Gravy 
• Soups
• Add to pasta or pasta sauce
• Use in a slow cooker meal
• Pizza toppings
• Use in a salad
• Make frittata or quiche
• Top your steaks or chicken

These are just a few ideas for putting those cooked onions to use. These are not limitations. Even with cooked onions, you could do just about anything you want to with them. 

In order to prevent being disappointed when you reheat those onions, there are some things you should know. 

Reheating onions is really a pretty simple process. Your onions may not be crisp or crunchy, but chances are you already planned on that if you cooked them to begin with. The exception here would be fried onions, like onion rings or onion blossoms. 

Let’s talk about properly storing cooked onions. 

Proper Storage of Cooked Onions

From here forward, you will see instruction for 2 variations of cooked onions. One group will be cooked onions in general. This could refer to sautéed onions or caramelized onions or anything along those lines. The other group will be fried onions. 

We separate these because they are slightly different and they could have slightly different instructions for reheating. Fried onion varieties typically have breading that must be considered for both storage and reheating purposes. 

Cooked onions cover a pretty broad category. You can cook onions in many different ways. Whether you sautéed them in butter or you cooked them in some other method, the following instructions cover the general category. 

Instructions for storing your cooked onions covers both regularly cooked onions and variations of fried onions. The recommended storage methods between these are primarily the same, which is great because that makes this step nice and easy. 

It really does not matter how you cooked your onions. These universal instructions cover the whole nine yards. 

You can store your cooked onions in either the refrigerator or the freezer, depending on how long you plan to store them. 

Storing Cooked Onions in the Refrigerator

Here is the thing to watch for when you store your onions and try to reheat them. Onions have their own moisture. This will play a part more with fried onions but we have some tricks for you when we get there. 

Here are instructions for storing cooked onions in the refrigerator. 

1. Allow cooked onions to cool to room temperature.
2. Store onions in the refrigerator within 2 hours of cooking. 
3. Seal tightly in a small airtight container or a sealing storage bag. 
4. Cooked onions will store in the refrigerator for 3-5 days. 

Storing Cooked Onions in the Freezer

If 3-5 days just isn’t long enough, you can make your onions last a little longer by storing them in the freezer. 

Here are your instructions for storing onions in the freezer:

1. Allow cooked onions to cool to room temperature. Be sure you prepare them for storage within 2 hours of cooking. 
2. Place cooked onions in either heavy-duty freezer bags or small airtight containers. 
3. Place in freezer for up to 12 months. 

Now, let’s get down to business! 

Reheating Cooked Onions

There are separate reheating methods for cooked onions and fried onions. Cooked onions reheat best on the stovetop while fried onions reheat best in the oven. 

The instructions we provide are best-practice instructions. You could also potentially use the microwave to reheat either type of onion but it is not recommended for the best results. 

Reheating Cooked Onions (Not Fried)

This set of instructions is specifically for onions that were not fried when originally cooked. 

Our recommended cooking method is the stovetop as it will revive your onions appropriately. There is no need to thaw your onions from the freezer prior to reheating. However, you can if you prefer to. 

1. Heat butter or oil in a skillet at medium to high heat. If your onions already have plenty of moisture from a sauce you can skip this but we recommend still using a small amount in a warm pan. 
2. Add your onions to the heated skillet. 
3. Cook for about 5 minutes, stirring frequently. 
4. Your onions are finished when they are heated thoroughly. 

Reheating Cooked Onions (Fried)

Now we focus on the recommended process for fried onions variations. With fried onions, again you do not have to defrost them but you can. 

The recommended reheating process is completed through the oven. 

1. Cover a baking sheet with foil. 
2. Preheat your oven to 440-450 degrees. The high heat is what will help maintain the crispness. 
3. Spread your onions over the baking sheet. You can grease it lightly if you like. You can also spray cooking spray over the tops of the onions as well. This is optional. 
4. Bake in the oven for 10-15 minutes. Flip them about halfway through cooking time. 

Related Questions

We hope you find this guide to be a valuable resource for reheating any cooked onions you may be working with. 

We invite you to review our question and answer section for some additional details that may be beneficial to you. 

Can You Boil Your Onions?

Yes, you can boil onions. You put water and onions in a pan and bring to a boil. You then reduce heat and simmer 30-45 minutes until they are tender.

For reheating purposes, we still recommend using the stovetop directions provided for this type of cooked onion. 

Can My Stored Onions Be Poisonous?

Onions become poisonous if you do not closely follow the storage and reheating instructions. If you leave them at room temperature for too long, that is where the primary risk comes from.

This is because at room temperature they are more susceptible to bacteria. This is also a more likely risk of raw onion, not cooked.