Bacon Croissant Breakfast Casserole

There’s something magical about breakfast casseroles that I just can’t get over. They’re the perfect answer to feeding a crowd without standing over the stove flipping eggs one at a time. And when you use buttery croissants instead of regular bread? You’ve just taken things to a whole new level.

I started making this croissant breakfast casserole a few years ago when I had leftover croissants from brunch. The flaky layers soak up the custard perfectly, creating this rich, almost custardy texture that plain bread just can’t match. Plus, the Gruyere and bacon combo makes it taste fancy without any extra work on your part.

The best part is you can assemble this the night before and pop it in the oven while you’re making coffee. Whether it’s Christmas morning, a birthday brunch, or just a lazy Sunday when you want something special, this casserole delivers every single time.

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What Kind of Croissants Should I Use?

For this breakfast casserole, you’ll want to use day-old or slightly stale croissants if you can – they’ll soak up the egg mixture better without getting too soggy. Fresh croissants from your local bakery are great, but honestly, the ones from the grocery store bakery section work just fine too. If you only have fresh croissants on hand, you can leave them out on the counter overnight or pop them in a low oven for about 10 minutes to dry them out a bit. Butter croissants are your best bet here since they add richness to the casserole, but plain ones will work in a pinch.

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Options for Substitutions

This breakfast casserole is pretty forgiving when it comes to swaps:

• Croissants: Day-old croissants actually work better since they soak up the egg mixture nicely. If you can’t find croissants, use brioche, challah, or even French bread cut into chunks. Just keep in mind that croissants give this dish its signature buttery richness.
• Bacon: Swap bacon for breakfast sausage, ham, or turkey bacon if you prefer. You can also make this vegetarian by using sautéed mushrooms or leaving out the meat entirely.
• Gruyere cheese: Gruyere adds a nutty flavor, but Swiss cheese is a close match. You could also use all cheddar, Monterey Jack, or a combination of whatever melty cheeses you have on hand.
• Heavy cream: If you don’t have cream, use all milk instead – just know the texture will be slightly less rich. Half-and-half also works as a middle ground.
• Fresh sage: No fresh sage? Use 2 teaspoons of dried sage instead, or try fresh thyme or rosemary for a different herb flavor.
• Dijon mustard: Yellow mustard or whole grain mustard both work fine here. You can also skip it if mustard isn’t your thing.

Watch Out for These Mistakes While Baking

The biggest mistake you can make with this casserole is using fresh, soft croissants instead of day-old ones – stale croissants hold their shape better and won’t turn mushy when you pour the egg mixture over them.

Another common error is undercooking the bacon, which will steam in the oven and become rubbery rather than crispy, so make sure it’s fully cooked and crispy before adding it to the dish.

Don’t skip the resting time after baking, as pulling the casserole straight from the oven will cause it to fall apart when you try to serve it – those 5-10 minutes allow the eggs to set properly.

Finally, press down gently on the croissant pieces with a spatula after pouring the egg mixture to ensure every piece gets soaked, otherwise you’ll end up with dry spots that didn’t absorb enough custard.

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What to Serve With Croissant Breakfast Casserole?

This casserole is pretty rich and filling on its own, so I like to serve it with something fresh and light on the side. A simple fruit salad with berries, melon, and grapes is always a hit at brunch and helps balance out all that cheesy goodness. You could also go with a mixed green salad tossed with a light vinaigrette, or even some sliced tomatoes with a sprinkle of salt and pepper. If you’re feeding a crowd for a special breakfast or holiday brunch, add some hash browns or roasted potatoes to make it even more of a feast.

Storage Instructions

Store: Leftover croissant breakfast casserole keeps really well in the fridge for up to 4 days. Just cover it tightly with plastic wrap or transfer individual portions to airtight containers. It makes breakfast so easy during the week when you can just grab a piece and go!

Make Ahead: This casserole is actually perfect for making the night before. Assemble everything, cover it with foil, and stick it in the fridge overnight. In the morning, just pull it out, let it sit at room temperature while your oven preheats, then bake as directed. You might need to add 5-10 extra minutes to the baking time since it’s coming from the fridge.

Freeze: You can freeze this casserole either before or after baking for up to 2 months. If freezing unbaked, assemble it in a freezer-safe dish and wrap it really well. Thaw overnight in the fridge before baking. For already-baked casserole, cut it into portions and wrap individually for easy grab-and-go breakfasts.

Reheat: Warm up individual portions in the microwave for about 1-2 minutes, or reheat the whole casserole covered with foil in a 350°F oven for 15-20 minutes. The croissants might not be quite as crispy as when freshly baked, but it still tastes great.

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 4200-4700
• Protein: 150-175 g
• Fat: 290-330 g
• Carbohydrates: 230-260 g

Ingredients

For the casserole:

• 9 large croissants (torn into 2-inch pieces)
• 8 oz bacon (I prefer Applegate Sunday Bacon for its smokiness)
• 1.25 cups Gruyere cheese (shredded, gives better texture and moisture)
• 1/2 cup cheddar cheese
• 8 large eggs
• 2 cups milk (I like Organic Valley whole milk for richness)
• 1 cup cream
• 2.5 tbsp sage
• 2.5 tsp mustard
• 1 tsp salt
• 1/4 tsp pepper
• Pinch of nutmeg

For the garnish:

• chives (finely sliced into tiny rings)

Step 1: Prepare the Mise en Place and Preheat

• 9 large croissants
• 1.25 cups Gruyere cheese
• 1/2 cup cheddar cheese
• chives

Preheat your oven to 350°F and grease a 9×13 inch baking dish (or similar size) with butter or cooking spray.

While the oven heats, tear the croissants into 2-inch pieces and set aside.

Shred the Gruyere and cheddar cheeses together in a bowl, then finely slice the chives into tiny rings and set both aside.

This prep work ensures everything is ready when you need it and prevents any scrambling during assembly.

Step 2: Cook the Bacon Until Crisp

• 8 oz bacon

Cut the bacon into bite-sized pieces and cook in a large skillet over medium-high heat for 4-5 minutes, stirring occasionally, until the bacon is crispy and the fat has rendered.

Transfer the cooked bacon to a paper towel-lined plate to drain briefly.

I like using high-quality bacon like Applegate because it adds a deeper, smokier flavor that really elevates the casserole’s savory profile.

Step 3: Build the Casserole Base

• cooked bacon from Step 2
• half of the shredded cheese mixture from Step 1
• torn croissants from Step 1

Spread the cooked bacon from Step 2 evenly across the bottom of your prepared baking dish, then sprinkle half of the shredded cheese mixture from Step 1 over the bacon.

Distribute the torn croissant pieces evenly over this layer, pressing down gently so they’re snug but not compressed.

This layering creates pockets that will soak up the custard and distribute flavor throughout the dish.

Step 4: Prepare and Pour the Custard Mixture

• 8 large eggs
• 2 cups milk
• 1 cup cream
• 2.5 tbsp sage
• 2.5 tsp mustard
• 1 tsp salt
• 1/4 tsp pepper
• Pinch of nutmeg

In a large bowl, whisk together the eggs, milk, cream, sage, mustard, salt, pepper, and nutmeg until well combined and smooth.

Pour this custard mixture evenly over the croissant layer, making sure to distribute it throughout so every piece gets soaked.

I prefer using whole milk and heavy cream because they create a richer, more luxurious custard that keeps the casserole moist as it bakes.

Step 5: Top and Bake the Casserole

• remaining shredded cheese mixture from Step 1
• assembled casserole from Steps 3-4

Sprinkle the remaining shredded cheese mixture from Step 1 evenly over the custard layer.

Transfer the baking dish to your preheated 350°F oven and bake for 40-45 minutes until the top is golden brown and a knife inserted into the center comes out clean or with just a few moist crumbs.

The custard should be set but still slightly creamy, not rubbery.

Step 6: Rest and Finish with Fresh Chives

• sliced chives from Step 1

Remove the casserole from the oven and let it rest for 5-10 minutes—this allows the custard to set slightly and makes serving cleaner and easier.

Scatter the sliced chives from Step 1 over the top just before serving for a fresh, bright finish that contrasts beautifully with the rich, savory casserole.

Bacon Croissant Breakfast Casserole

Delicious Bacon Croissant Breakfast Casserole recipe with step-by-step instructions.

Print Recipe Pin Recipe

Prep Time 20 minutes mins

Cook Time 35 minutes mins

Total Time 55 minutes mins

Servings 8 servings

Calories 4450 kcal

Ingredients

  

For the casserole::

• 9 large croissants (torn into 2-inch pieces)
• 8 oz bacon (I prefer Applegate Sunday Bacon for its smokiness)
• 1.25 cups Gruyere cheese (shredded, gives better texture and moisture)
• 1/2 cup cheddar cheese
• 8 large eggs
• 2 cups milk (I like Organic Valley whole milk for richness)
• 1 cup cream
• 2.5 tbsp sage
• 2.5 tsp mustard
• 1 tsp salt
• 1/4 tsp pepper
• Pinch of nutmeg

For the garnish::

• chives (finely sliced into tiny rings)

Instructions

 

• Preheat your oven to 350°F and grease a 9x13 inch baking dish (or similar size) with butter or cooking spray. While the oven heats, tear the croissants into 2-inch pieces and set aside. Shred the Gruyere and cheddar cheeses together in a bowl, then finely slice the chives into tiny rings and set both aside. This prep work ensures everything is ready when you need it and prevents any scrambling during assembly.
• Cut the bacon into bite-sized pieces and cook in a large skillet over medium-high heat for 4-5 minutes, stirring occasionally, until the bacon is crispy and the fat has rendered. Transfer the cooked bacon to a paper towel-lined plate to drain briefly. I like using high-quality bacon like Applegate because it adds a deeper, smokier flavor that really elevates the casserole's savory profile.
• Spread the cooked bacon from Step 2 evenly across the bottom of your prepared baking dish, then sprinkle half of the shredded cheese mixture from Step 1 over the bacon. Distribute the torn croissant pieces evenly over this layer, pressing down gently so they're snug but not compressed. This layering creates pockets that will soak up the custard and distribute flavor throughout the dish.
• In a large bowl, whisk together the eggs, milk, cream, sage, mustard, salt, pepper, and nutmeg until well combined and smooth. Pour this custard mixture evenly over the croissant layer, making sure to distribute it throughout so every piece gets soaked. I prefer using whole milk and heavy cream because they create a richer, more luxurious custard that keeps the casserole moist as it bakes.
• Sprinkle the remaining shredded cheese mixture from Step 1 evenly over the custard layer. Transfer the baking dish to your preheated 350°F oven and bake for 40-45 minutes until the top is golden brown and a knife inserted into the center comes out clean or with just a few moist crumbs. The custard should be set but still slightly creamy, not rubbery.
• Remove the casserole from the oven and let it rest for 5-10 minutes—this allows the custard to set slightly and makes serving cleaner and easier. Scatter the sliced chives from Step 1 over the top just before serving for a fresh, bright finish that contrasts beautifully with the rich, savory casserole.