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Cheesy Onion Casserole

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Sweet onions are the star of the show with this cheesy onion casserole. As the onions bake, they get soft and mild, making them the perfect base for herbs, cheese, and a buttery cracker topping.

Plate of cheesy onion casserole with softened rings of onions and buttery cracker topping, ready to eat.

This tasty onion casserole is a perfect side dish for holidays, Sunday suppers, and more. The oven brings 9 simple ingredients together in the most wonderful way.

This one just might even win over non-onion lovers. Because if ever there was a way to win someone over, cheese and a crumb topping are likely involved.

Ingredients including large sweet onions, butter, Ritz crackers, thyme, garlic salt, paprika, black pepper and cheese ready to be made into onion casserole.

I am always on the hunt for fun new side dish recipes. For whatever reason, coming up with fun sides is the hardest part of meal planning for me.

It is too easy to get into a run with veggies. We tend to keep them simple, but that gets boring after a while.

So armed with a couple of giant sweet onions, it seemed like a good time to turn them into a casserole. After all, cheesy cabbage casserole has won over a cabbage hater or two. Why couldn’t we come up with something that could do the same for onions.

I looked online for a recipe that would do the trick, but I didn’t find what I was looking for. So, I developed this one instead.

Why You’ll Love This Casserole

As the name suggests, sweet onions are usually on the milder side to start with. However, cooking them down makes them even more mild and delicious.

There is no onion bite in this recipe. So even folks who don’t think they like onions may just become fans.

A lot of onion casserole recipes require you to sauté the onions for a while first. This recipe lets the oven do the work so there are fewer dishes and less active cooking time.

Some garlic salt, mustard powder, thyme, and paprika add some depth of flavor to the dish. The butter and cheese bring that rich goodness and keep the onions tender and delicious.

I used a mix of gruyere and smoked gouda in the casserole. They both have good flavor but aren’t too sharp.

That allows the onions to really shine through. However, you can use whatever good melting cheeses you like.

I am sure cheddar would be delicious. Monterey jack, Swiss, or provolone would all be tasty options as well.

Covering the casserole dish with foil and allowing the onions and cheese to have a nice long trip to the oven gives the onions a chance to soften nicely. It takes some time, but no actual effort once it is in the oven.

Once the onions are tender, it’s time to add the topping. Because after all, what is a casserole without some sort of crunchy topper?

Here, we opted to use some buttered cracker crumbs. We love cornflake topped casseroles, but the buttery texture of Ritz crackers seemed like a better option for this particular recipe.

Bake it a little bit longer to toast the cracker crumbs and finish it off, and it is time to dig in. Be prepared to fall in love after the first bite!

Close up of baked onion casserole, showing texture of the crackers and onions.

Frequently Asked Questions

What are the best onions to use in the casserole?

Any sweet onion will work well. You could use white or yellow onions in a pinch, but they may result in a stronger onion flavor.

Can I make this gluten free?

Of course! Just use gluten free crackers for the topping. Or you could use potato chips, pork rinds, or your favorite casserole topper.

How do I store the leftovers?

Leftover casserole can be stored in an airtight container in the refrigerator for up to 4 days. Just reheat them for about 30 seconds in the microwave to serve. Freezing the casserole would affect the texture, and is not recommended.

Large serving spoon filled with onion casserole, ready to go on dinner plate.

Tips and Tricks

This recipe works well in a 9×13-inch pan. You could make half of the recipe in an 8-inch square.

For a more rustic presentation, make the casserole in a 12-inch cast iron skillet.

Don’t worry if the pan looks really full when you put the onions in. They will shrink down as they cook.

Onion casserole served with BBQ pork chop and cowboy salad.

I like the look of leaving the onions in rings. However, you can rough chop them or julienne them if you prefer.

This casserole goes great with turkey, ham, or roast beef. It is also great with grilled entrees. We loved it with BBQ pork chops and cowboy salad.

More Great Cheesy Side Dish Casseroles

Cheese and crackers also star in fresh pineapple casserole. It’s a sweet and salty side dish that sounds strange but tastes amazing.

Cheesy onion casserole served on small plate with remaining casserole in background.

Of course, it is hard to go wrong with funeral potatoes. A pan or two of those cheesy potatoes make an appearance at almost every holiday meal.

Corn casserole with cheese and green chiles is another wonderful option. It adds a little bit of spice to one of our all-time favorite sides.

For more inspiration, check out my collection of side dish recipes. There is sure to be something there you’ll love.

Plate of cheesy onion casserole with softened rings of onions and buttery cracker topping, ready to eat.

Cheesy Onion Casserole

Servings: 12 Servings
Author: Carlee
Sweet onions are the star of the show with this cheesy onion casserole. As the onions bake, they get soft and mild, making them the perfect base for herbs, cheese, and a buttery cracker topping.
4.91 from 11 ratings
Prep Time 10 minutes
Cook Time 1 hour 5 minutes
Total Time 1 hour 15 minutes


  • 3 lb. sweet onions
  • 1 teaspoon garlic salt
  • ½ teaspoon mustard powder
  • ½ teaspoon dried thyme
  • ½ teaspoon paprika
  • ¼ teaspoon ground black pepper
  • 4 Tablespoons butter divided
  • 1 cup shredded gruyere
  • 1 cup shredded smoked gouda
  • 1 sleeve Ritz crackers or similar


  • Preheat oven to 350°F and grease a 9×13-inch pan.
  • Remove the ends and skins from the onions cut into rings about 1/2-3/4-inch wide. Arrange onion rings in prepared pan.
    3 lb. sweet onions
  • Mix together the seasonings and sprinkle over onions. Top with shredded cheese.
    1 teaspoon garlic salt, ½ teaspoon mustard powder, ½ teaspoon dried thyme, ½ teaspoon paprika, ¼ teaspoon ground black pepper, 1 cup shredded gruyere, 1 cup shredded smoked gouda
  • Cut half of the butter into thin slices and distribute over cheese.
    4 Tablespoons butter
  • Cover the pan tightly with foil and bake for 50 minutes. The onions should look softened.
  • Melt the remaining butter. Crush the crackers into crumbs and toss in the melted butter. Sprinkle over the casserole.
    1 sleeve Ritz crackers
  • Bake for 15 more minutes, this time uncovered. The crackers should be golden and the onions should be nice and soft.
  • Enjoy warm.


Serving: 1servingCalories: 144kcalCarbohydrates: 9gProtein: 6gFat: 10gSaturated Fat: 6gPolyunsaturated Fat: 3gCholesterol: 31mgSodium: 315mgFiber: 1gSugar: 6g

Nutritional Disclaimer

“Cooking With Carlee” is not a dietitian or nutritionist, and any nutritional information shared is an estimate. If calorie count and other nutritional values are important to you, we recommend running the ingredients through whichever online nutritional calculator you prefer. Calories and other nutritional values can vary quite a bit depending on which brands were used.

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Recipe Rating


Monday 29th of May 2023

I made this last night and followed the recipe exactly and we loved it! I'm going to use some of the leftovers for an appetizer this afternoon on crostini. I love dishes that easily transform into a new dish. Went great with your tequila lime grilled chicken recipe :)


Monday 29th of May 2023

YAY!!!! I am so glad you liked it. And the chicken too, now I want to make both recipes again myself!

Karen @karenskitchenstories

Saturday 20th of May 2023

I'm a huge onion fan so this is right up my alley. Plus, I need an excuse to buy some Ritz.


Saturday 20th of May 2023

This is the perfect excuse!

Andrea Nine

Friday 19th of May 2023

I love onions and cheese so I’m in!


Friday 19th of May 2023

It's really good. Even LD liked it, and he isn't an onion fan.