Sweet Onion Casserole
The spotlight is on onions in this classic sweet onion casserole! Using a few simple ingredients and easy to make ahead of time, it’s the perfect dish for a weeknight side or potluck.
Ever heard of a 1015 onion? I had no idea there are so many different onions around, LOL. Aside from white, red, yellow, Spanish, and Vidalia, of course.
Once called the sweetest onion in the world after being discovered by Texas A&M horticulture professor Dr. Leonard Pike, it’s still a popular onion.
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’s 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!
More Sweet Onion Recipes
One of my favorite smells coming from the kitchen is simmering onions and garlic in a pan with some olive oil. I made a joke to my husband that they should turn it into a perfume, LOL. If you like onions as much as I do, you will love these onion recipes.
- French Onion Meatballs
- French Onion Dip
- French Onion Chicken Skillet
- German Onion Pie
- Baked Onion Dip
See recipe card for complete information on ingredients and their quantities.
Ingredient Notes
- Sweet onions – Vidalia onions, 1015 onions, or mild yellow onions are the best.
- Swiss cheese – Cheddar cheese is a great substitute if you don’t like Swiss. I have tested this with Mozzarella and Monterey Jack too and it turns out delicious!
- Saltine crackers – Substitute Ritz, other buttery cracker, or Panko bread crumbs. I have even made this with Corn Flakes and I love the crunch!
- Evaporated milk- Substitute heavy cream or half & half.
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How To Make Onion Casserole Recipe
- Preheat oven to 350 F. Chop onions into thin slices (around ½ inch). In a large skillet, melt butter over medium-high heat. Add onion slices to the skillet and stir. Saute onions until tender.
- In a prepared baking dish, place half of onions. Top with half the Swiss cheese and 3/4 cup of the cracker crumbs. In a small bowl, combine eggs, milk, and seasonings. Pour over cooked onions and cheese.
- Layer with the remaining half of chopped onions and top with the remainder from your cup of the cheese. Mix melted butter with the remainder of the cracker crumbs.
- Spread over top of casserole. 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 cooking instructions, please see the recipe card at the end of this post.
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.
Storage & Reheating
This casserole will last in the fridge for up to 3 days, as long as it’s placed in an airtight container.
Reheat in the microwave or the oven (350F) until heated through. If it seems dry when reheating, add in a little chicken broth.
How To Prep Ahead
This is a great casserole to make ahead of time! Cook your onions as directed, then transfer them to a covered casserole dish and store it in the fridge for up to 3 days.
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.
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.
1015 Casserole
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
- Preheat oven to 350F.
- In a large skillet, saute the onions in the ¼ cup butter over medium heat until tender.
- Layer ½ the onion mixture in bottom of a 8×8 baking pan.
- Cover with 1 cup Swiss cheese.
- Top with 3/4 cup saltine crumbs.
- Add remaining onions in a layer and top with remaining cheese.
- In a bowl, combine the eggs, milk, and seasonings.
- Pour over onion layers.
- Melt 3 tablespoons butter and mix with remaining cracker crumbs.
- Spread over top of casserole.
- 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
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You can’t go wrong with this casserole. I works with everything I’ve made it with!
SO delicious! We love it and will be making this again
My daughter who is an onion LOVER, devoured this dish. Will be making it again.
This is a new favorite. Even the guys loved it and they aren’t the biggest onion fans.
I’ve never heard of this recipe but couldn’t wait to try it and it was even better than I could have imagined. It will be a regular on our dinner table!
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!
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!
You can always remove the salt from the recipe to suit your needs. The onions have plenty of flavor!