Spinach and Gruyère Breakfast Casserole

Why You’ll Love This Recipe

I love how this casserole balances hearty and delicate flavors. The custard is gently seasoned with nutmeg and brightened by a hint of lemon zest, while the Gruyère melts into every bite for a subtle richness. It’s vegetarian, make-ahead friendly, and absolutely perfect for holiday mornings, weekend brunches, or even breakfast-for-dinner nights.

Ingredients

(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)

• Fresh spinach (sautéed until wilted and squeezed dry)

• Gruyère cheese, grated

• Eggs

• Whole milk

• Heavy cream

• Bread (day-old or toasted, cubed)

• Onion or shallot, finely chopped and sautéed

• Freshly grated nutmeg

• Lemon zest

• Salt and pepper

• Butter (for greasing the baking dish)

Directions

1. I start by sautéing the spinach in a bit of olive oil until just wilted, then I let it cool and squeeze out as much moisture as possible. I chop it roughly and set it aside.

2. I sauté onion or shallot in the same pan until softened and fragrant.

3. In a large bowl, I whisk together eggs, milk, cream, nutmeg, lemon zest, salt, and pepper to create the custard base.

4. I fold in the cubed bread, spinach, sautéed onion, and most of the grated Gruyère, mixing until everything is evenly coated.

5. I pour the mixture into a buttered baking dish, then sprinkle the top with the remaining cheese.

6. I cover and refrigerate the casserole for at least 8 hours, or overnight, to let the bread absorb the custard fully.

7. When ready to bake, I let the dish sit at room temperature while preheating the oven to 350°F (175°C).

8. I bake uncovered for about 1 hour and 40 minutes, or until the top is golden and the center is set.

9. I let it rest for at least 10 minutes before slicing and serving.

Servings and timing

This recipe serves 8 people.
Prep time: 10 minutes
Cook time: 1 hour 40 minutes
Chill time: At least 8 hours (overnight recommended)
Resting time: 10 minutes
Total time: 1 hour 50 minutes (plus chilling)
Calories per serving: Approximately 330 kcal

Variations

Sometimes I add sautéed mushrooms, roasted red peppers, or sun-dried tomatoes for more texture and flavor. If I want a stronger cheese flavor, I mix in some sharp white cheddar or fontina. I’ve also used sourdough or brioche when I want a richer base.

storage/reheating

Leftovers keep well in the fridge for up to 3 days. I reheat individual portions in the oven or toaster oven at 325°F until warmed through. The microwave works too, but I prefer the texture from the oven.

FAQs

Can I use frozen spinach?

Yes, I thaw and squeeze it very dry before mixing it in. It’s a great shortcut when fresh spinach isn’t available.

What kind of bread works best?

I use a sturdy day-old bread like sourdough, French bread, or a rustic country loaf. Soft sandwich bread may get too mushy.

Can I bake it right away instead of chilling overnight?

It’s possible, but I’ve found the flavor and texture improve with overnight soaking. At minimum, I let it rest for 1 hour before baking.

How do I know when it’s done?

The casserole should be puffed, golden, and set in the center. I test with a knife—if it comes out clean or with a few moist crumbs, it’s ready.

Can I make this gluten-free?

Yes, I’ve substituted gluten-free bread with good results. I just make sure it’s a denser style so it holds up well in the custard.

Conclusion

This spinach and Gruyère breakfast casserole is a make-ahead marvel that’s both comforting and refined. The silky custard, tender greens, and melty cheese come together beautifully, making it a standout for brunch or any time I want to serve something special with ease. It’s one of those dishes that looks as good as it tastes—and tastes even better the next day.

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