Vidalia Onion Casserole

4.95 from 60 ratings

Make onions the STAR of the show with this classic Southern sweet onion casserole! This version uses sweet onions, has 9 ingredients, and can be made in advance for a yummy weeknight side dish with grilled chicken or as part of a Thanksgiving or Easter dinner. Bonus points for this being a Ritz Cracker topped casserole! (aka the best kind)

close up of ritz cracker topping on onion casserole.

Onion casserole. Heard of it? Had it? It's new-ish to me; my MIL brought us a version she made earlier this summer with just "I'm bringing onion casserole" and I just immediately knew I had found my new favorite veggie side dish.

I love a casserole, as we well know. I also really like onions, and sweet onions + cheesy stuff + Ritz cracker topping? Count.Me.In.

(By the way, two casseroles in one dinner is NEVER a bad thing; a squash casserole is another great Ritz-topped side dish that we love!)

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Recipe Notes
Ingredients
Ingredient Notes
Onion Casserole Recipe FAQ
How to Make Onion Casserole: Step By Step Instructions
Other Vegetable Side Dishes
Did You Try This One Yet?
Recipe

Recipe Notes

This is one of those super simple casserole recipes with one little step that takes awhile: halfway caramelizing the onions. After that, we mix soft, sweet, mostly cooked onions with cheese and sour cream and spices, top with crackers, and bake into submission.

I need to tell you that the end result of this onion casserole recipe is SO MUCH MORE than the sum of its parts. Onions are cheap, humble, and flavorful but often used to flavor other things. This caramelized, sweet, cheesy casserole, though, is just WOWOWOW. Doesn't feel like a throwaway ingredient at all. Makes you want to do more things with onions always.

The point, of course, is that adding cheese + dairy + crackers to literally any vegetable is a good method.

Not to be bossy, but this is really good as a side dish to crispy chicken thighs with leeks and lemon, just saying.

Ingredients

We need! Thinly sliced onions. Butter to cook them in. Cheddar cheese and grated parmesan cheese, mayo and sour cream for creaminess, crackers for topping. Salt and black pepper for flavor. Again, can't say enough how very simple this is.

Meal Prep Pro Tip: When slicing the onions for this recipe, slice a few extras and store them in the fridge for a few days, then use them in hibachi veggies for a quick easy rice bowl dinner!

Ingredient Notes

Casseroles always beg the question: can I make this casserole healthy? I mean...yes, but why not make grilled or roasted onions, instead? To me, casseroles have a certain mandatory creaminess that works using full-fat dairy ingredients, in the amounts the recipe calls for.
I wouldn't use low fat or fat free dairy. You could use all sour cream or all mayo, but it would change the flavor a little bit.
You can definitely substitute another melty cheese in place of the cheddar like Swiss or provolone - both are really yummy.
Serving: This casserole goes with so many main dishes: in particular I like this as a side dish to smoked turkey with a roasted sweet potato and snappy asparagus. A VERY good dinner, yes yes yes.

thanksgiving plate with turkey and sides close up.

Onion Casserole Recipe FAQ

Which Onions Are Best for Casseroles?

I like sweet onions for this casserole - Vidalia or anything labeled sweet. However, regular yellow or white onions would work fine for this dish; the end result may just be a bit sharper. I've used both and as long as you cook the onions down properly, they'll sweeten up and be delicious.

Can I Make This In Advance?

YES AND YES. Highly encouraged, in fact. Make the casserole all the way to the last baking step, then cover and keep in the fridge for up to 4 days. When you're ready to eat, bake the casserole until it's hot and bubbly. If you want to go full Martha on your meal prep, chop some extra onions and use them after Thanksgiving in leftover turkey and dumplings (made with canned biscuits because we are TIRED, ok?)

Can I Make This Gluten Free?

Sure can! Just use a GF topping like GF crackers or crushed potato chips.

What Can I do With Too Many Yellow Onions?

Um, hello, absolutely this onion casserole recipe! Of course, onions keep a long time so it's not usually important to use them right away, but onion casserole is a GREAT way to get rid of too many onions.

How to Make Onion Casserole: Step By Step Instructions

The Thing That Takes Time with this recipe is slicing and caramelizing the onions. We only cook the onions about halfway, but it still takes 45 minutes or so of low and slow, just a little bit of stirring, to soften the onions before we assemble the casserole.

For the onions, heap them in a skillet with the butter and some salt and pepper. Let the onions cook gently over low heat for 45-60 minutes until they're translucent and very soft.

raw sliced onions in a skillet with butter and pepper.

During this time, keep an eye on the heat. If the onions aren't cooking at all, increase the heat to medium. If they sizzle and start to brown, turn the heat way back. The onions will reduce and release their liquid but shouldn't be browning like in a stir fry.

When the onions are done, combine them with the rest of the casserole ingredients - everything but the crackers. I do this in the skillet, but you can transfer everything to a large mixing bowl if you prefer.

filling for onion casserole in white skillet.

Taste the onion mixture here and add more salt and pepper if you'd like - everything should be mixed together smoothly and taste REALLY good.

Scrape the onion casserole mixture into a baking dish, and sprinkle the Ritz crackers all over the top. At this point, you can cover the casserole and keep in the in the fridge for a few days, or bake it right away for eating.

unbaked vidalia onion casserole in baking dish.

To cook, bake the casserole uncovered for 357F until hot and bubbly all the way through. If, during baking, the crackers start to get too brown, place a piece of foil over the casserole loosely to avoid burning the topping.

Casserole = done! I can't say it enough, the creamy center, mild onion flavor, and crunchy cracker topping is everything I love about a casserole, perfect for Thanksgiving, Easter, Sunday dinner, or any time a cozy, comforting side dish is called for.