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Cheesy Onion Casserole Recipe

Cheesy Onion Casserole is a delicious side dish recipe idea that quickly becomes the star of the show on any table! Onion lovers will enjoy the sweet onion flavor and lots of cheese!

Cheesy Onion Casserole Recipe

Cheesy Onion Casserole is a super easy side dish recipe you can make for the holiday season or any night of the week!

You’ll love this creamy recipe that is filled with Vidalia onions (or sweet onions when Vidalia’s are out of the season!), a ton of cheese, cream of mushroom soup, and a few other pantry staples.

This simple recipe takes the complicated Thanksgiving dishes, and makes them the perfect side dish for any special occasion you’re celebrating!

It’s a low-carb and keto diet-friendly recipe!

How to Make Cheesy Onion Casserole

First, let’s gather the ingredients.

You’ll need a ton of sweet onions. If it’s the precious summertime, and you have access to Vidalia onions, get those!

sweet onions

You’ll need about 3 pounds of onions total before you skin the onions and slice them.

If you don’t have access to a Vidalia sweet onion, choose a sweet onion or yellow onion. I’ve never tried this with red onions, but I bet it would be good! Not as sweet, but still delicious!

Otherwise, those large sweet onions you see in the produce section, that are the size of a softball will work perfectly!

Next, you’ll need a bunch of shredded cheese. 4 cups worth! This is where I use up any and all the cheese in my fridge. If I have the bags of pre-shredded cheddar cheese, I’ll dump them in. Same with swiss cheese, mozzarella, parmesan cheese, etc.

Then you’ll need a cup of mayonnaise, a can of cream of mushroom soup, and half a can of milk. If you want to add a little sour cream, feel free to! It gives the recipe a little tang that quickly makes this a family favorite!

Now, let’s gather the dried spices you’ll use in the recipe:

  • Parsley
  • Chives
  • Thyme
  • Onion Powder
  • Garlic Powder
  • Salt
  • Black Pepper

If you’re feeling frisky, add a little cayenne pepper or red pepper flakes!

onion casserole recipe

Cooking the Onions

Peel and slice your onions about 1/4-1/2 inch thick, in half moons.

Melt butter in a large saute pan and add in a couple of tablespoons of olive oil. This helps the butter not to burn and adds in some extra moisture to the onions.

Then in a large skillet soften the onion slices over medium heat with butter and olive oil.

You don’t want the onions to caramelize, just turn them a little brown and soften them.

While the onions are cooking in a saute pan, let’s mix up the cheese and soup mixture.

tennessee onions

To a large mixing bowl, add your shredded cheese, mayonnaise, mushroom soup, and half a can of milk. And if you’re feeling really decadent, use heavy cream!

Mix all of that up so everything is evenly distributed.

Add your seasoning on top, and give another good mix using a spatula.

Once the onions are softened, pour the onions over the soup mixture.

Baking the Onion Casserole

After the onions have been combined with the cheese mixture, pour them into a buttered casserole pan.

If you want some crunch, add a sleeve of crushed Ritz Crackers to the top of the casserole before baking!

Bake at 350˚ for 30-35 minutes, or until the top is golden brown and bubbly.

creamy onion casserole

This Vidalia onion casserole pairs well with Grandma’s Roasted Turkey on Thanksgiving, or a big Beef Tenderloin for Christmas Dinner!

Save this to your favorite Side Dish Board on Pinterest!

Cheesy Onion Casserole
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Cheesy Onion Casserole Recipe

  • Author: Sweetpea
  • Prep Time: 20
  • Cook Time: 30
  • Total Time: 50 minutes
  • Yield: 8 1x
  • Category: side dish
  • Method: oven-baked
  • Cuisine: southern


Cheesy Onion Casserole is a side dish recipe idea that becomes the star of the show on any table! Onion lovers will enjoy the sweet onion flavor!


  • 3 lbs. Sweet Onions, sliced into 1/4‘1/2 inch half moons
  • 2 TBS Butter
  • 2 TBS Olive Oil
  • 4 cups Shredded Cheese
  • 1 cup Mayonnaise
  • 1 can Cream of Mushroom Soup
  • 1/2 can Milk
  • 1 tsp Parsley
  • 1 tsp Chives
  • 1/2 tsp Thyme
  • 1 tsp Garlic Powder
  • 1 tsp Onion Powder
  • 1/2 tsp Kosher Salt
  • 1/2 tsp Black Pepper


  1. Peel and slice your onions.
  2. In a large skillet, over medium heat, melt 2 tablespoons of butter and 2 tablespoons of olive oil.
  3. When the butter is foamy, add in your sliced onions, and stir.
  4. Cover and let soften for 10-15 minutes, stirring occasionally.
  5. In a large mixing bowl, add in your 4 cups of shredded cheese, 1 cup of mayonnaise, 1 can cream of mushroom soup, and 1/2 can of milk. Mix all of this together.
  6. Add in your one teaspoon of parsley, one teaspoons of chives, half a teaspoon of thyme, one teaspoon garlic powder, one teaspoon onion powder, half a teaspoon of kosher salt, and half a teaspoon of black pepper. Mix well.
  7. Once the onions are soft, pour them over the cheese and soup mixture — mixing to combine well.
  8. Pour into a buttered casserole dish (9×13 works great!), and bake at 350˚ for 30-35 minutes, on until the top is golden brown and bubbly.


You can use any shredded cheese you like, this recipe uses cheddar and mozzarella. But, it’s a great time to use up any leftover cheese in your fridge!

If you want to make this a few days before serving, cover with plastic wrap before baking, and store in the fridge. Allow the baking dish to come to room temperature before baking according to the directions.

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