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.

1015 Onion Casserole Recipe

Ever heard of a 1015 onion? For me, I didn’t know there are that many different onions around, LOL.

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!

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.

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How to Make Onion 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.

5. In a small bowl, combine eggs, milk, and seasonings. Pour over cooked onions.
6. Grab melted butter and mix with the remainder of the cup of cracker crumbs. Spread over top of casserole. 
7. 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.

More Sweet Onion Recipes

• French Onion Meatballs
• French Onion Dip
• French Onion Chicken Skillet
• German Onion Pie
• Baked Onion Dip

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.

Can I make it 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.

Serving Suggestions

This southern sweet onion casserole is best served with a simple side dish like sweet potatoes, a veg all casserole recipe, 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!

Easy Vegetable Casserole Recipes

Vegetable casseroles are great for when you have a Meatless Monday or just need a side dish to go with a rotisserie chicken or some burgers. I make this one all the time!

Some of my other favorites are this Brenda Gantt cabbage casserole, this Joanna Gaines sweet potato casserole, and this Captain Crunch sweet potato casserole.

Tips for the Best Casserole

• 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!

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.

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

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