Overnight Croissant Breakfast Casserole Recipe

Jump-start your morning with this indulgent Overnight Croissant Breakfast Casserole! Layers of buttery croissants, savory sausage, sautéed veggies, and rich, melty Gruyère cheese come together in a velvety custard—ready to bake after an overnight rest in your fridge. Whether you’re hosting brunch or just need a delicious fuss-free breakfast for a busy week, this casserole practically guarantees happy faces at the table.

Why You’ll Love This Recipe

• Effortless Mornings: Prep everything ahead of time, and all that’s left is a quick bake in the morning—no bleary-eyed measuring or frantic scrambling!
• Seriously Irresistible Flavors: Buttery croissants soak up eggs and cream, seasoned with garlic and packed with sausage, peppers, and Gruyère. Each bite is warm, creamy, and full of cozy comfort.
• Perfect for a Crowd: Whether it’s for family or friends, this casserole feeds a tableful, making it ideal for holidays, weekend get-togethers, or anytime you’ve got guests.
• Flexible and Forgiving: Don’t have sausage? Use bacon. Prefer cheddar over Gruyère? Swap away. Want to sneak in some extra veggies? Go for it.
• Texture Heaven: Toasting the croissants first is a revelation—expect a beautifully creamy center with those unbeatable crispy, golden edges.

Ingredients You’ll Need

Here’s what brings this dreamy breakfast together:

• Croissants: The star of the show. Their rich, buttery layers soak up the custard, becoming pillowy inside while crisping up on top. Use stale or day-old croissants for best soak and texture.
• Breakfast Sausage: Adds hearty, savory flavor. Choose your favorite—pork or turkey both work. Cook it and crumble before adding.
• Olive Oil: For sautéing the vegetables, bringing extra richness.
• Onion: Provides a subtle sweetness and depth as it cooks down.
• Red & Green Bell Peppers: Bring pops of color and gentle sweetness.
• Eggs: The base of your custard. They bind all the ingredients together and turn pillowy as they bake.
• Whole Milk & Half-and-Half: Creamy richness—don’t skimp here! The combination yields a tender, luscious custard.
• Gruyère Cheese: Melts beautifully and adds a nutty flavor. Shred your own for the best melt—pre-shredded just isn’t the same.
• Kosher Salt & Black Pepper: Essential for seasoning, highlighting all the other flavors.
• Garlic Powder: Just a touch to boost savoriness. If you love garlic, you could use fresh, but the powder blends seamlessly.
• Unsalted Butter: Greasing the baking dish and adding flavor—don’t skip this step for easy casserole release!

Variations

Love making a dish your own? Here are some tasty spins:

• Vegetarian Version: Leave out the sausage and add sautéed mushrooms or chopped spinach for an earthy twist.
• Change the Cheese: Swap Gruyère for sharp cheddar, fontina, Swiss, or even crumbled feta, depending on what you’ve got.
• Add Some Heat: Sprinkle in red pepper flakes or diced jalapeño with the peppers for a breakfast casserole with a gentle kick.
• Other Proteins: Ham or crisp bacon work beautifully in place of sausage.
• Gluten-Free Option: Use gluten-free croissants or sturdy, gluten-free bread as a substitute.
• Brighter Flavors: Toss in chopped sun-dried tomatoes or fresh herbs like chives or parsley for freshness.

How to Make Overnight Croissant Breakfast Casserole

Step 1: Prep the Croissants

Tear croissants into hearty, bite-sized pieces and toast them in the oven until golden—this crucial step keeps them from getting soggy and makes the casserole’s texture absolutely divine.

Step 2: Cook the Fillings

Brown breakfast sausage in a skillet, then sauté diced onion and both bell peppers in olive oil until soft and fragrant. This combo fills your kitchen with savory aromas that signal something amazing is on the way.

Step 3: Make the Custard

In a large mixing bowl, whisk together eggs, whole milk, half-and-half, garlic powder, salt, and pepper. You want everything smooth and well blended.

Step 4: Combine Everything

Stir in cooked sausage, sautéed veggies, and most of the grated Gruyère into the egg mixture. Add the toasted croissants last, making sure everything gets thoroughly moistened—no dry spots!

Step 5: Chill and Rest

Spread the mixture in a buttered baking dish, pouring any remaining custard over the top. Cover with parchment (to prevent sticking) and a layer of foil, then let it chill for at least an hour—or overnight. This rest is non-negotiable! It lets the croissants soak up every bit of flavor.

Step 6: Bake to Perfection

Let the dish sit at room temperature for 30 minutes before baking. Sprinkle the remaining cheese over the top, then bake covered until almost set. Uncover and finish baking until golden, puffed, and irresistibly fragrant. Let it rest briefly before serving—the hardest part is waiting!

this Recipe

Pro Tips for Making the Recipe

• Don’t Skip Toasting Croissants: This keeps them from going mushy—if you cheat on this step, you lose all that luxurious texture!
• Let It Rest: Chilling overnight is magic. It melds flavors together and ensures a perfectly custardy interior.
• Shred Your Cheese Fresh: The melt and flavor are leaps ahead of pre-shredded.
• Test for Doneness: The casserole should be puffed and set in the center, with no visible liquid. Slight jiggle is good, but runny is not.
• Customize, But Stick to the Ratio: Too many add-ins can make it soggy—keep the veg and meat totaled to about 2–2½ cups.

How to Serve

This casserole is a stand-alone stunner, but it shines even brighter with thoughtful sides:

Fresh Finishers

• Sprinkle fresh chives, parsley, or green onions for a pop of color and flavor.
• Serve with sliced avocado, a dollop of sour cream, or your favorite hot sauce.

Pairings

• Pair with a bright fruit salad for freshness.
• Serve with a light arugula or mixed greens salad dressed with lemon vinaigrette to cut through the richness.
• Strong coffee or mimosas are more than welcome at the table!

Make Ahead and Storage

Storing Leftovers

Seal leftovers in an airtight container and store in the refrigerator for 2–3 days. The flavors actually get even better!

Freezing

This casserole freezes beautifully. Wrap portions tightly in foil, then store in a freezer-safe bag or container for up to 4 weeks.

Reheating

To reheat, place wrapped casserole in a 350°F oven for 5–10 minutes, or until warmed through. You’ll get the best texture using the oven over the microwave.

FAQs

Can I use other kinds of bread if I don’t have croissants?
Absolutely! Brioche or challah are solid substitutes, offering that same rich texture. Just make sure to toast them as you would the croissants to prevent sogginess.

Do I really need to let it rest overnight in the fridge?
While a full overnight rest is ideal, you can get away with as little as one hour if you’re short on time. That said, overnight chilling makes the flavors meld and guarantees the best croissant texture.

Can I assemble and bake it the same day?
Technically, yes, if you give it at least an hour in the fridge. But rushing misses the magic—plan ahead and you’ll be rewarded with a superior casserole.

What’s the best way to keep the casserole from sticking to the pan?
Generously butter the baking dish, and use a piece of parchment on top before adding foil to cover. This keeps the cheese from pulling off when you remove the foil, ensuring a beautiful golden top every time.

Final Thoughts

This Overnight Croissant Breakfast Casserole is the secret weapon for stress-free, spectacular mornings. It’s easy, endlessly customizable, and always a crowd-pleaser. Whether you’re feeding loved ones or just craving something delicious, you’re guaranteed a breakfast worth waking up for. Try it once—and you’ll be hooked!

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