Creamy French Onion Broccoli Cheese Casserole with caramelized onions, broccoli, Gruyère, cheddar, and a crispy panko topping. Cozy, comforting, and perfect for cold nights.

You ever have one of those days where the weather feels… indecisive? Like it wants to rain, but also maybe hail, or just hover there with that stubborn gray sky that looks like a screensaver from the early 2000s? That was me, standing in the kitchen, hungry in that way where you want something warm but don’t totally know what. I remember picking up two onions and a head of broccoli and thinking, “Okay, universe, what exactly am I making here?” And I swear there was this split-second where the idea for a French Onion Broccoli Cheese Casserole just clicked — kind of like when you suddenly remember the name of an actor at 2 a.m.

I’d been craving the comfort of French onion soup but also wanted something more… substantial? Something that didn’t require bread toasted under a broiler while I worried about burning it (again). So I started caramelizing onions, which honestly always makes me feel like I have my life just a tiny bit together, even if everything else is chaos. And when the Gruyère melted into that warm sauce like it was auditioning for a romantic drama, I got weirdly sentimental in a way that’s probably embarrassing to admit. Ever get emotional over cheese? Please tell me I’m not alone.

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What surprised me most was how this French Onion Broccoli Cheese Casserole tasted like something I’d eaten during family holidays, even though I’d literally invented it on the spot. There’s something about broccoli wrapped in a velvety cheese sauce next to those jammy onions that feels nostalgic. And now it’s one of those dishes people ask me to bring to gatherings… which is flattering until I realize they’re not actually asking about me, they’re asking about the casserole. Happens to the best of us, right?

Why You’ll Love This French Onion Broccoli Cheese Casserole Recipe?

Okay, so here’s the thing. This casserole is the kind of comfort food that sneaks up on you. At first glance, it looks simple — broccoli, onions, cheese — nothing wild. But then you take a bite and suddenly you’re having a whole emotional experience you didn’t plan for. The caramelized onions bring that deep, sweet-savory vibe that honestly reminds me of cozy restaurants during winter where everything smells like butter and nostalgia. Then the broccoli steps in, like the responsible friend who says, “Hey, here’s some fiber,” but in a non-annoying way.

And the cheese sauce? Let’s just say there are days when I wonder if melted cheese could solve at least half the world’s problems. Maybe not all, but a good chunk. The best part is how this French Onion Broccoli Cheese Casserole strikes that balance between “wow, this tastes fancy” and “did I really just make this in under an hour?” Do you ever feel slightly suspicious when something tastes better than the amount of effort you put into it? Because same.

Ingredient Notes:

Let’s talk ingredients for a second, because each one plays a role in this French Onion Broccoli Cheese Casserole like a character in a sitcom where everyone’s personality somehow fits together perfectly.

• Olive oil + butter: These two together? Foolproof. It’s like mixing business with pleasure — but in a good way.

• Yellow onions: Thinly sliced because we want them to caramelize, not fight us. Onions are dramatic, so let them have their moment.

• A pinch of sugar: Not enough to make it sweet, just enough to help the onions hit that golden “I’m ready” stage.

• Garlic + thyme: The duo that walks in halfway through the episode and steals the scene.

• Flour + butter (roux): Don’t panic at the word roux. It’s just flour cooked in butter. If you’ve ever made gravy, you’ve basically done this.

• Beef broth + milk: Depth plus creaminess. Like a buddy-cop duo with surprisingly good chemistry.

• Broccoli: Blanched so it stays bright green and doesn’t give the casserole that “oops, I forgot to drain this” watery texture.

• Gruyère + sharp cheddar: The cheeses that make people ask, “What did you put in this?”

• Panko + butter: The crunchy topping that makes everyone go quiet for a second while they process happiness.

How To Make French Onion Broccoli Cheese Casserole?

Let’s walk through this together — pretending we’re in the kitchen, wearing comfortable socks, maybe listening to a playlist from 2014 because why not.

Step 1. Prep your baking dish.
Grease the dish. Set it aside. Easy. We’re easing into things.

Step 2. Caramelize the onions.
This is where the magic starts. Melt the butter with olive oil, toss in the onions, salt, and sugar, and just… let them relax. Stir now and then. Let them get golden and soft. Honestly, they’ll tell you when they’re ready. Add garlic and thyme for the final minute. Heavenly.

Step 3. Blanch the broccoli.
This is quick — two minutes in boiling water, then drain like your life depends on it. Excess water is the enemy of casseroles everywhere.

Step 4. Make the cheese sauce.
Butter, flour, whisk. Add broth, then milk. Let it thicken. Then comes the cheese moment — Gruyère and cheddar melting into a sauce that smells like you’ve been cooking for three hours, not three minutes.

Step 5. Assemble.
Broccoli + onions + cheese sauce = the trio you didn’t know you needed. Mix gently in your dish and top with the rest of the cheddar.

Step 6. Add the panko topping.
Butter + panko + parsley. Mix it up and sprinkle generously. Don’t be shy.

Step 7. Bake.
18–22 minutes. Bubble, golden top, the kind of smell that makes the neighbors jealous. Let it rest because hot cheese is basically lava.

Storage Options:

This French Onion Broccoli Cheese Casserole holds up really well — like, weirdly well. Store leftovers in the fridge up to three days. The flavors deepen overnight in that “I didn’t expect this to be better but it totally is” kind of way. Reheat in the oven to get the crispy top back, though the microwave works if you’re impatient (no judgment). You can also freeze it, which is basically future-you sending present-you a thank-you note.

Variations and Substitutions:

Cooking isn’t a test; it’s more like jazz. You improvise. This French Onion Broccoli Cheese Casserole can handle it.

• Swap Gruyère for Swiss, provolone, or fontina.

• Add cooked chicken or leftover ham.

• Make it vegetarian with vegetable broth.

• Use gluten-free flour and GF panko easily.

• Add mushrooms for even more French onion flavor.

• Stir in rice or pasta if you want it heartier.

Ever made a recipe your own by accident? Same. Honestly, half my best dishes happened because I was out of something important.

What to Serve with French Onion Broccoli Cheese Casserole?

This dish pairs well with:

• A simple green salad

• Roasted chicken or turkey

• Crusty bread (for scooping — don’t pretend you won’t do it)

• White wine, especially something crisp like Sauvignon Blanc

But honestly? You could eat this French Onion Broccoli Cheese Casserole alone in pajamas and it would taste just as good.

Frequently Asked Questions:

Can I freeze it?
Yep — and it reheats beautifully.

Can I use frozen broccoli?
Yes, but thaw and drain like your sanity depends on it.

My topping didn’t brown — help?
Broil for a minute. But don’t walk away. Trust me.

If you try this French Onion Broccoli Cheese Casserole — or if you end up tweaking it into some wild, wonderful version — I hope you tell me. I love seeing how recipes grow once they leave my kitchen.

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French Onion Broccoli Cheese Casserole

Prep Time 20 minutes mins

Cook Time 35 minutes mins

Total Time 55 minutes mins

A rich and comforting French Onion Broccoli Cheese Casserole made with caramelized onions, crisp broccoli, a creamy Gruyère–cheddar sauce, and a buttery panko topping. Perfect for holidays, potlucks, or cozy weeknight dinners.

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8 Servings

Ingredients

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• 1 tablespoon olive oil
• 2 tablespoons unsalted butter for onions
• 2 large yellow onions thinly sliced
• 1/2 teaspoon granulated sugar
• 1 teaspoon kosher salt divided
• 2 garlic cloves minced
• 1/2 teaspoon dried thyme
• 2 tablespoons unsalted butter for roux
• 2 tablespoons all-purpose flour
• 1 cup low-sodium beef broth
• 1 cup whole milk
• 4 cups broccoli florets blanched and well-drained
• 6 ounces Gruyère cheese shredded
• 1 cup sharp cheddar cheese shredded, divided
• 1/2 teaspoon ground black pepper
• 1 cup panko breadcrumbs
• 2 tablespoons unsalted butter melted (for topping)
• 1 tablespoon fresh parsley chopped (optional)

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Instructions

 

Prepare the baking dish.

1. Preheat the oven to 375°F. Grease a 9×13-inch baking dish and set aside.

Caramelize the onions.

1. In a large skillet, heat the olive oil and 2 tablespoons butter over medium-low heat. Add the sliced onions, 1/2 teaspoon of the kosher salt, and the granulated sugar. Cook, stirring occasionally, until the onions become deeply golden and caramelized, approximately 20–25 minutes. Add the garlic and thyme; cook for an additional 1 minute. Remove from heat.

Blanch the broccoli.

1. Bring a pot of salted water to a boil. Add the broccoli florets and cook for 2 minutes, until bright green and crisp-tender. Drain thoroughly and pat dry to prevent excess moisture in the casserole.

Prepare the cheese sauce.

1. In a medium saucepan, melt 2 tablespoons butter over medium heat. Add the flour and cook, whisking continuously, for 1 minute to form a roux. Slowly whisk in the beef broth, followed by the milk. Simmer, whisking frequently, until the sauce thickens, 3–4 minutes. Remove from heat and stir in the Gruyère and half of the cheddar cheese until smooth. Season with the remaining 1/2 teaspoon salt and the black pepper.

Assemble the casserole.

1. In the prepared baking dish, combine the blanched broccoli, caramelized onions, and cheese sauce. Stir gently to distribute the ingredients evenly. Sprinkle the remaining cheddar cheese across the top.

Prepare the breadcrumb topping.

1. In a small bowl, combine the panko breadcrumbs with the melted butter (and parsley, if using). Distribute the mixture evenly over the surface of the casserole.

Bake.

1. Bake for 18–22 minutes, or until the casserole is bubbling and the topping is golden brown. Allow the casserole to rest for 5–10 minutes before serving.

Notes

To make this French Onion Broccoli Cheese Casserole gluten-free:

• Use gluten-free all-purpose flour when preparing the roux.
• Select gluten-free panko breadcrumbs for the topping.
• Ensure the beef broth is labeled gluten-free.
• All other listed ingredients are generally gluten-free but verify packaging to be certain.

Bitty

DID YOU MAKE THIS RECIPE?Let me know! Mention @nodashofgluten or tag #nodashofgluten

Bitty

I’m Bitty, owner of nodashofgluten.com, where I share simple, delicious recipes for all tastes, including gluten-free. Check out my “About Me” page for more info!

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