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Sweet Onion Casserole

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The spotlight is on onions in this classic 1015 Casserole! Paired with simple ingredients and easy to make ahead of time, it’s the perfect dish for a weeknight side or potluck.

original recipe of 1015 casserole coming out of a white dish

1015 Casserole Recipe 

Ever heard of a 1015 onion? Once called the sweetest onion in the world after being discovered by Texas A&M horticulture professor Dr. Leonard Pike, it’s still a favorite of onion lovers.

But if you don’t live in Texas like me, this is a great recipe with any sweet onion I can get ahold of. For me in Georgia, it’s the Vidalia. I could eat them raw they are so tasty.

Because they are so good, I made them to star of this casserole that is perfect for so many occasions.

But my favorite is for busy weeknights because you can easily prep this one ahead of time and bake when ready.

I love sweet onions so much I used them in my French Onion Chicken Casserole!

overhead picture of ingredients for onion casserole on a marble backdrop

Ingredients Needed

  • Large sweet onions – Vidalia onions or yellow onions are the best.
  • Swiss cheese – Cheddar cheese is a great substitute.
  • Saltine crackers – Substitute Ritz, other buttery cracker, or Panko bread crumbs.
  • Eggs – Use large eggs at room temperature.
  • Evaporated milk- Substitute heavy cream or half & half.
  • Pantry Staples – Unsalted butter, salt, and black pepper.

How To Make 1015 Casserole

  1. Preheat oven to 350 F. Chop large Tennessee onions into thin slices (around ½ inch slices).
  2. In a large skillet, melt butter over medium-high heat. Add onion slices to the skillet and stir. Saute onions until tender.
  3. In a prepared baking dish, place half of onions. Top with half the Swiss cheese and 3/4 cup of the cracker crumbs.
  4. Layer with the remaining half of chopped onions and top with the remainder from your cup of the cheese.
  1. In a small bowl, combine eggs, milk, and seasonings. Pour over cooked onions.
  2. Grab melted butter and mix with the remainder of the cup of cracker crumbs. Spread over top of casserole. 
  3. Bake in the preheated oven for a total time of 20 – 25 minutes or until golden brown on top. 

For the full recipe and detailed baking instructions, please see the recipe card at the end of this post.

baked 1015 casserole in a white dish with blue checkered napkin

What do I serve with 1015 Onion Casserole?

This southern sweet onion casserole is best served with a simple side dish like sweet potatoes or a baked potato with sour cream and chives.

If you want to lighten it up, a fresh chopped salad with homemade Italian dressing is great!

How long does it last?

This casserole will last in the fridge for up to 3 days, as long as it’s placed in an airtight container.

If it seems dry when reheating, add in a little chicken broth to moisten.

Can I make this ahead of time?

Yes, this is a great casserole to make ahead of time. Cook your onions as directed, before placing them in a covered casserole dish and putting it in the fridge.

The cracker topping is easy to make ahead of time and stored in a plastic bag until it’s time to make your casserole.

When you’re ready, just assemble according to the instructions and enjoy.

dish of 1015 casserole with a scoop missing

Best Casserole Tips

  • It’s easier to cut the onion in half and then slice. But you can slice them into whole onion rings if you like.
  • Make sure to spray your casserole dish with a nonstick cooking spray to prevent sticking.
  • If you want maximum crunch for your topping, try crushing up potato chips in a medium bowl before coating the top if your casserole.
  • Add in parmesan cheese or sharp. cheddar cheese mixed with a tablespoon butter to create a more cheesy topping.
  • To cut your onions without crying, try putting wet paper towels next to you to absorb the acid that the onions release. Another trick is to freeze or chill your onions, rather than cutting them at room temperature.
  • Add in a pinch of brown sugar and a dash of soy sauce for a richer flavor.

If you love this recipe as much as I do, pin this to your favorite casserole Pinterest board and share it on your favorite social media channels!

casserole with scoop missing and blue banner with text "sweet onion 1015 casserole"

This sweet onion casserole recipe is a staple in the lone star state, and is about to become a staple in your home as well. Not only is it easy to make but it brings that comfort food feel to your dinner table, and pairs well with a number of side dishes.

overhead picture of 1015 casserole in square white dish

1015 Casserole

Yield: 9 servings
Prep Time: 10 minutes
Cook Time: 25 minutes
Total Time: 35 minutes

This sweet onion 1015 Casserole is full of tangy Swiss cheese, sweet 1015 onions, and layers of buttery crackers, baked to perfection!

Ingredients

  • ¼ cup unsalted butter
  • 3 large sweet onions, peeled and sliced
  • 2 cups shredded Swiss cheese, divided
  • 1 ½ cups crushed saltine crackers, divided
  • 2 large eggs, room temperature
  • ¼ cup evaporated milk
  • 1 teaspoon salt
  • ½ teaspoon pepper
  • 3 tablespoons unsalted butter

Instructions

    1. Preheat oven to 350F.
    2. In a large skillet, saute the onions in the ¼ cup butter over medium heat until tender.
    3. Layer ½ the onion mixture in bottom of a 8x8 baking pan.
    4. Cover with 1 cup Swiss cheese.
    5. Top with 3/4 cup saltine crumbs.
    6. Add remaining onions in a layer and top with remaining cheese.
    7. In a bowl, combine the eggs, milk, and seasonings.
    8. Pour over onion layers.
    9. Melt 3 tablespoons butter and mix with remaining cracker crumbs.
    10. Spread over top of casserole.
    11. Bake at 350F for 20-25 minutes or until bubbly and the topping is golden brown.

Notes

  • It's easier to cut the onion in half and then slice. But you can slice them into whole onion rings if you like.
  • Make sure to spray your casserole dish with a nonstick spray to prevent sticking.
  • If you want maximum crunch for your topping, try crushing up potato chips in a medium bowl before coating the top if your casserole.
  • Add in parmesan cheese or sharp. cheddar cheese mixed with a tablespoon butter to create a more cheesy topping.
  • To cut your onions without crying, try putting wet paper towels next to you to absorb the acid that the onions release. Another trick is to freeze or chill your onions, rather than cutting them at room temperature.
  • Add in a pinch of brown sugar and a dash of soy sauce for a richer flavor.
Nutrition Information:
Yield: 9 Serving Size: 1
Amount Per Serving: Calories: 271Total Fat: 18gSaturated Fat: 11gTrans Fat: 0gUnsaturated Fat: 6gCholesterol: 89mgSodium: 375mgCarbohydrates: 18gFiber: 1gSugar: 7gProtein: 10g

This nutrition information was generated via a third party, Nutritionix, and we can not be held liable for any discrepancies in the information provided.

More Sweet Onion Recipes

{Originally published 08/12/22 – photos/recipe notes updated to improve reader experience 08/30/23}

BestCasseroleRecipes.com. Content and photographs are copyright protected. Sharing of this recipe is both encourages and appreciated. Copying and/or pasting full recipes to any social media is strictly prohibited.

Rita Scott

Friday 10th of November 2023

We need to watch our salt intake. Is the 1 tsp. of salt needed or could it be reduced or even eliminated? I want to try this as we do like our onions, plus they are healthy really. Well, perhaps, butter, cheese & saltines... Oh my!

jennifer

Tuesday 14th of November 2023

You can always remove the salt from the recipe to suit your needs. The onions have plenty of flavor!

Michaela Kenkel

Thursday 18th of August 2022

OMG!! We LOVED this casserole! A friend told me about your website and I have so many recipes printed already. Casseroles are my favorite comfort food and we just got a new favorite with this one!

Tristin

Wednesday 17th of August 2022

My daughter who is an onion LOVER, devoured this dish. Will be making it again.

Mindy

Tuesday 16th of August 2022

SO delicious! We love it and will be making this again

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