Southern onion casserole is the kind of side dish that quietly steals the show. Sweet, tender onions are baked in a creamy, cheesy filling and topped with buttery Ritz cracker crumbs until golden and crisp. It's easy enough for Sunday dinner but absolutely belongs in the Thanksgiving sides list or on the Christmas table, especially since you can assemble it ahead of time and bake it when you're ready.
If you think onions belong in the background, bless your heart. This old-fashioned casserole gives them the starring role, and frankly, they've been waiting long enough.
Table of Contents
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🥰 Is this Southern onion casserole recipe for you?
- You believe onions deserve main-character status instead of being chopped up and told to support everybody else.
- You love creamy, cheesy Southern side dishes with plenty of buttery Ritz cracker crumbs on top.
- You need something that works just as well with Sunday dinner as it does with Thanksgiving turkey or Christmas ham.
- You appreciate a casserole you can assemble ahead of time and bake when you're ready.
- You want an old-fashioned comfort food recipe made with simple ingredients and absolutely no unnecessary culinary gymnastics.
🧾 Ingredients
Sweet onions are essential here, so grab Vidalia, Walla Walla, or another sweet variety and let them have their moment.
- Onions - Sweet onions are the move here. Vidalia, Walla Walla, or Maui all work beautifully. Regular yellow onions will do in a pinch, but the flavor will be sharper.
- Butter - Because onions and butter have been carrying Southern cooking on their backs for generations. Why end a great partnership now?
- Evaporated milk - Richer and creamier than regular milk without making the casserole soupy.
- Eggs - Hold the whole glorious onion situation together while it bakes.
- Mozzarella - Melts into the casserole and gives you that gooey, cheesy stretch we came here for.
- Cheddar - Use sharp cheddar and grate it from the block. We have standards.
- Ritz crackers - Some go inside, some get buttered and scattered over the top. Ritz understands the assignment.
- Salt and pepper - Onions are naturally sweet, so don't get timid with the salt. Pepper keeps everybody respectable.
📖 Recipe
Southern Onion Casserole
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- 4 large onions, sliced to ¼-inch thickness, about 1 ½ pounds of onions
- 2 tablespoons butter
- 3 eggs
- ⅔ cup evaporated milk, 5 ounces
- 1 cup Ritz cracker crumbs
- 1 ½ cups grated cheddar cheese, grate from a block
- ½ cup Mozzarella, grated from a block.
- 1 teaspoon salt
- ¼ teaspoon black pepper
Topping:
- 1 cup Ritz cracker crumbs, coarsely crushed
- 3 tablespoons butter, melted
Instructions
- Grease a 13x9 inch pan.
- Preheat the oven to 375F.
- Place onions in a saucepan and cover with water.
- Bring to a boil and simmer until tender - about 6-8 minutes.
- Drain and put back in the pan.
- Stir in butter.
- In a large mixing bowl whisk the eggs and evaporated milk together until combined. Add the onion and butter mixture.
- Stir in the Ritz cracker crumbs, grated cheddar cheese, grated Mozzarella, salt, and pepper.
- Add to prepared 13x9-inch pan.
- Combine topping ingredients in a small mixing bowl and sprinkle on top of the mixture in the prepared pan.
- Bake for 40-45 minutes, or until heated through. It will register 165F on an instant read thermometer.
Notes
- Cut ¼ inch thick for best results.
- Don't let the onions get too soft while simmering. Just cook them until you can easily pierce them with a fork, about 6-8 minutes.
- Try substituting Cheez-Its for the Ritz sometime.
Nutrition Facts
Nutrition information is estimated as a courtesy. If using for medical purposes, please verify information using your own nutritional calculator. Percent Daily Values are based on a 2000 calorie diet.
This recipe has been tested several times. If you choose to use other ingredients, or change the technique in some way, the results may not be the same.
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🔪 How to make Southern onion casserole
Grab a big bowl and your favorite casserole dish and get started.
- Simmer the onions until softened.
- Drain onions and stir in butter.
- Combine eggs and evaporated milk.
- Add onions, crackers, and the cheese.
- Stir well to combine the onion mixture.
- Mix topping ingredients in a small bowl.
- Spoon onion mixture into dish and add topping.
- Bake at 375 degrees F for 40-45 minutes.
😱 What can go wrong (and how to fix it)
🧅 The casserole is watery. Drain those onions really well after simmering. They hold more water than you'd think, and nobody invited onion soup to this particular gathering.
🧅 The onions turned to mush. You only want them tender enough to pierce easily with a fork. Six to eight minutes should do it. We're making casserole, not onion purée.
🧅 The onions are still crunchy. Give them another minute or two on the stove before draining. They should be tender before they ever see the casserole dish.
🧅 The cheese is greasy instead of creamy. Grate your cheddar and mozzarella from the block. Pre-shredded cheese has a coating that keeps it from melting as smoothly, because apparently even cheese comes with complications.
🧅 The Ritz topping is soggy. If you're assembling the casserole ahead, leave the topping off until you're ready to bake. Add those buttery crumbs at the last minute so they stay crisp.
🧅 The top is getting too brown. Loosely cover the casserole with foil for the rest of the baking time. Don't tuck it in. Just give it a little aluminum sunbonnet.
🧅 The center doesn't seem done. Check it with an instant-read thermometer. You're looking for 165°F in the center before you pull it from the oven.
👩🍳 FAQs
Sure. Most Spanish onions are on the sweeter side, though they won't be quite as sweet as varieties like Vidalia or Walla Wallas.
I don't recommend it. The flavor and texture won't be right. Red onions are best fresh, like on salads, tacos, and sandwiches.
It's simple. Just swap the Ritz crackers for your favorite gluten-free butter cracker. They likely won't taste quite as crisp as regular crackers, but it'll do the trick.
Nope, evaporated milk is thicker and less liquidy than regular milk. If you are absolutely in a pinch and need a last-minute swap, you could try heavy cream or cream cheese, instead.
📚 More favorite southern sides
If onion casserole has earned a spot on the table, these old-fashioned Southern sides probably belong there, too.
🏡 Southern onion casserole is one of those recipes that makes you wonder why onions have spent all these years being treated like supporting characters. Sweet onions, plenty of cheese, and that buttery Ritz topping make a very convincing argument for giving them the whole casserole dish.
Make it for Sunday dinner, put it next to the turkey at Thanksgiving, or bring it to Christmas dinner and watch the onion skeptics suddenly develop opinions about who gets the last spoonful.
Kathy says
Thank you for sharing this recipe
Wanda Saathoff says
All your recipes has my mouth watering! I can't wait to get in the kitchen and try the majority of them...