French Onion Broccoli Cheese Bake

French Onion Broccoli Cheese Bake brings together everything comforting in one warm, bubbling dish. First, sweet caramelized onions melt into a creamy cheese sauce. Then, tender broccoli adds freshness and balance. As a result, every bite feels rich yet familiar. Moreover, this bake works beautifully as both a cozy side and a satisfying vegetarian main.

French onion flavors trace back centuries, originally created as a humble, affordable comfort food. Over time, however, the combination of slow-cooked onions and melted cheese became iconic. Today, that same depth of flavor shines in modern casseroles like this one. Meanwhile, broccoli keeps the dish vibrant and hearty without feeling heavy.

Because it’s baked until golden and bubbling, this recipe fits perfectly into holidays, weeknight dinners, or casual entertaining. Best of all, it comes together with simple ingredients. Once you try it, it quickly becomes a repeat favorite.

Recipe Yield: 6 servings

INGREDIENTS

4 cups broccoli florets, cut small
1 cup shredded sharp cheddar cheese
¾ cup shredded Gruyère cheese
¼ cup grated Parmesan cheese
2 large yellow onions, thinly sliced
2 tbsp unsalted butter
2 tbsp olive oil
1 tsp sugar
1 tsp kosher salt
½ tsp black pepper
2 cloves garlic, minced
2 tbsp all-purpose flour
1½ cups whole milk
½ cup heavy cream
1 tsp fresh thyme leaves
½ cup crispy fried onions (plus extra for topping)

INSTRUCTIONS

1. Caramelize the onions:
First, melt butter with olive oil in a wide skillet over medium heat. Add onions, sugar, salt, and pepper. Cook slowly, stirring often, for 25–30 minutes until deeply golden and jammy. Add garlic during the last 1 minute.

2. Build the sauce:
Next, sprinkle flour over the onions and stir for 1 minute. Gradually whisk in milk and cream. Then add thyme and simmer 3–4 minutes until thickened.

3. Prepare the broccoli:
Meanwhile, steam broccoli just until fork-tender, about 4 minutes. Drain well.

4. Combine and enrich:
Afterward, fold broccoli into the sauce. Remove from heat and stir in cheddar, Gruyère, Parmesan, and fried onions until melted and creamy.

5. Bake to perfection:
Finally, transfer to a buttered baking dish. Top with extra fried onions. Bake at 375°F for 20–25 minutes until bubbly and golden. Rest 5 minutes before serving.

Helpful Tips to Perfect This Recipe

• Slow caramelization matters: Although tempting to rush, slow-cooked onions deliver deep French onion flavor and natural sweetness that elevates the entire bake.
• Small broccoli florets work best: Because they absorb sauce more evenly, every bite stays creamy, balanced, and indulgent.
• Layer your cheese wisely: Using both Gruyère and sharp cheddar adds depth, meltability, and that signature cozy finish people crave.