Ham and Cheese Croissant Breakfast Casserole (Make-Ahead Brunch)

I started making this casserole a few years ago when I needed something I could assemble the night before and just slide into the oven on a Saturday morning without thinking. We had a house full of people for Eid brunch, I was already making a dozen other things, and I needed one dish that could carry itself. This was it. Buttery croissants, smoky ham, sharp cheddar, and a simple egg custard — and when it comes out of the oven it looks like you spent your whole morning on it.

What makes this work is the croissants. They're not just bread — they have layers that soak up the egg mixture and then puff back up in the oven. The edges get a little crispy, the inside stays soft and custardy, and the cheese melts into every crevice. I've made egg casseroles with regular sandwich bread before and they're fine, but croissants take it somewhere else entirely. If you've ever made my Berry French Toast Casserole, you'll recognize the same logic — good bread transforms the whole thing.

My husband eats this with hot sauce on the side, which honestly works. Zainab picks out the ham pieces and eats them first, then goes back for the eggy croissant bits. Saad, predictably, wants it every weekend once he's had it once. I usually make a double batch when I know we have guests coming, because a single 9x13 disappears faster than I expect.

One thing to set expectations on: use croissants that are at least a day old if you can. Fresh-from-the-bag croissants are too soft and they turn mushy in the custard. Day-old ones hold their shape and still absorb everything. I buy a bag from Costco or Walmart a day before I plan to make this and leave them out overnight — works every time.

Why You'll Love This Recipe

• It comes together the night before: The whole point of this casserole is that the hard work happens when you have time — not at 7am when you're still half-asleep. I assemble it after dinner, cover it with plastic wrap, and put it in the fridge. In the morning I just preheat the oven and bake. No whisking eggs before coffee. That alone makes it worth making.

• The texture is genuinely different from regular egg bakes: I've made plenty of egg casseroles with sliced bread and they're good, but the croissant layers do something special. The tops of the croissant pieces crisp up and the undersides turn soft and custard-soaked. You get both textures in every serving, which regular bread just doesn't give you.

• It feeds a crowd without stress: A 9x13 dish cuts into 8–10 generous pieces easily. When I have family over for brunch, I pair it with some fruit and coffee and it's a full spread. I'm not standing at the stove flipping individual eggs — everything's already in the oven doing its thing while I sit with my guests.

• One pan, minimal cleanup: Everything goes into a single baking dish. Mix the eggs in one bowl, layer everything in the dish, pour it over, done. The washing up afterward is fast. On a brunch morning when I've already made tea and cut fruit, the last thing I want is a pile of pots.

• You can customize it with what you have: The base recipe is ham and cheddar, but I've made it with leftover rotisserie chicken, with Swiss cheese, with sautéed mushrooms thrown in — it adapts. The egg-custard-croissant ratio stays the same, so whatever you put in the middle is up to you.

Ingredients

• 6 large croissants, torn into bite-sized pieces (day-old works best)
• 8 large eggs
• 2 cups whole milk
• 1½ cups shredded cheddar cheese
• 1½ cups diced cooked ham
• 1 teaspoon Dijon mustard (optional, but I always add it)
• 1 teaspoon salt
• ½ teaspoon black pepper
• ½ teaspoon garlic powder
• 1 tablespoon butter, for greasing the baking dish

Directions

• Step 1: Grease the pan and tear the croissants. Preheat your oven to 350°F (175°C) and rub a 9x13-inch baking dish with butter. Tear the croissants into large chunks — not too small, you want some heft — and spread them out in an even layer in the dish. Don't pack them down; you want air pockets for the custard to settle into.
• Step 2: Add the ham and cheese. Scatter the diced ham evenly over the croissants, then cover the whole surface with the shredded cheddar. Make sure the cheese gets into the gaps between the pieces, not just sitting on top — it melts more evenly that way.
• Step 3: Make the egg custard. In a large mixing bowl, whisk together the eggs, milk, salt, pepper, garlic powder, and Dijon mustard until fully combined and a little frothy. Take your time with this — you want it smooth, no streaks of egg white running through it.
• Step 4: Pour and press. Pour the egg mixture slowly and evenly over the croissants. Press down gently with a spoon or your hands (I use my hands) so the croissants make contact with the liquid. Let it sit for 10 minutes so the bread can start absorbing. If you're doing this the night before, cover with plastic wrap and refrigerate overnight — this step is done for you by morning.
• Step 5: Bake uncovered. Bake uncovered at 350°F for 40–45 minutes until the top is golden brown and the center feels set when you gently shake the dish. If the top is browning too fast around the 25-minute mark, tent it loosely with foil and keep baking. Every oven is different.
• Step 6: Rest before slicing. Pull it out and let it sit for 5 minutes before you cut into it. This is annoying when it smells that good, but it firms up and slices cleanly instead of falling apart on the serving spatula.

Tips for Success

• Use day-old croissants, not fresh ones: I learned this the hard way the first time I made this casserole. I used croissants straight from the bag, they turned to mush, and the whole thing had no structure. Slightly stale croissants absorb the custard without disintegrating. If your croissants are fresh, leave them out on a wire rack overnight uncovered and they'll dry out just enough.

• Don't skip the resting time after pouring: That 10-minute rest before baking (or overnight in the fridge) is what lets the croissants soak up the egg mixture properly. If you pour and immediately put it in the oven, the top layer is dry and the bottom is wet. Give the custard time to move through the whole dish.

• Tent with foil if it's browning too fast: Croissant tops can go from golden to burnt quickly because of the butter in the pastry. I check mine at the 25-minute mark. If the surface is already deep brown but the center is still jiggly, I tent it loosely with foil for the remaining baking time. You want the inside set before the outside burns.

• Season the custard properly: Eggs need salt. The ham already has some salt, but don't rely on it to carry the whole dish. I use 1 teaspoon of salt in the egg mixture and it's well-seasoned without being salty. Taste your custard before you pour it — it should taste slightly salty on its own because the croissants will dilute it.

• If baking from cold, add extra time: When I bake this straight from the fridge after an overnight rest, I add 5–8 extra minutes to the baking time. Cold custard takes longer to set in the center. Don't pull it early just because the top looks done — jiggle the dish gently and the center should barely move, not slosh.

Variations

• Swap ham for bacon or breakfast sausage: Cook and crumble 6–8 strips of bacon or half a pound of breakfast sausage and use that instead of the ham. The smoky-savory flavor is different but equally good. I've done this when I had leftover bacon from a weekend breakfast and didn't want it to go to waste.

• Try Swiss or Gruyère instead of cheddar: Cheddar is my default because it's always in my fridge, but Swiss melts beautifully and has a slightly nuttier flavor that pairs really well with ham. Gruyère is the fanciest version — if you want something that tastes like a proper French croque monsieur in casserole form, go with Gruyère. You can also check out provolone for a milder, meltier option.

• Add sautéed vegetables: Mushrooms, spinach, or diced bell peppers work well here. Sauté them first to cook off the moisture — if you throw raw vegetables into the custard they release water as they cook and the casserole ends up wet. I usually do this when I want to stretch the dish a little further or sneak vegetables past Zainab.

• Make it spicy: Add a teaspoon of hot sauce to the custard, or scatter some diced jalapeños between the ham layer and the cheese. Pepper jack cheese instead of cheddar also does the job. My husband's version of this casserole always has extra heat — he adds Tabasco directly to his slice.

• Make it vegetarian: Leave out the ham entirely and double up on sautéed vegetables — mushrooms, spinach, roasted red peppers, or caramelized onions. Add extra cheese to make up for the missing protein bulk. It's a genuinely different dish and a good one.

Serving and Storage

Serving

Serve this warm, right out of the oven after its 5-minute rest. It pairs well with a simple fruit salad, some fresh-squeezed juice, or coffee. For a bigger brunch spread I'll put it alongside my Berry French Toast Casserole so there's a sweet option and a savory one — people always appreciate having both. A drizzle of Dijon cream (just Dijon stirred into a little sour cream) on the side is a nice touch if you want to dress it up.

Storage

Leftovers keep well in an airtight container in the fridge for up to 3–4 days. To reheat, microwave individual portions for 60–90 seconds, or put the whole dish back in a 300°F oven for about 15 minutes until warmed through. To freeze, let it cool completely, slice into individual portions, wrap each one tightly in plastic wrap, and freeze for up to 2 months. Thaw overnight in the fridge and reheat in the oven — the texture holds up better than you'd expect.

Frequently Asked Questions

Can I assemble this the night before and bake it in the morning?

Yes, and honestly the overnight soak makes it better. The croissants have more time to absorb the custard evenly, which means a more consistent texture throughout. Just cover the dish tightly with plastic wrap and refrigerate. In the morning, pull it out while the oven preheats and add 5–8 extra minutes to the baking time since it's starting cold.

Can I use store-bought croissants for this recipe?

Absolutely — I always do. The ones from Costco or Walmart work great. The key is that they should be a day old, not fresh. Fresh croissants are too soft and collapse into mush. Leave them out uncovered overnight or buy them a day ahead so they can dry out slightly before you use them.

What's the best cheese to use?

Cheddar is my go-to because it melts well and has enough flavor to hold up against the ham. Swiss and Gruyère are great if you want something a little more refined. Mozzarella works if you want a milder, stretchier result. The one cheese I'd skip is pre-shredded bagged cheese — it has anti-caking agents that prevent it from melting as smoothly. Buy a block and shred it yourself if you can.

How do I know when the casserole is fully cooked?

The top should be golden brown and when you gently shake the dish, the center should barely move — not slosh like liquid. If it's still very jiggly in the middle, give it another 5 minutes and check again. An instant-read thermometer in the center should read around 160°F (71°C) if you want to be precise about it.

Can I freeze this casserole?

Yes. Let it cool completely first, then slice into individual portions and wrap each one tightly in plastic wrap before putting in a freezer bag. It keeps well for up to 2 months. To reheat, thaw overnight in the fridge and warm in a 300°F oven for 15 minutes. I wouldn't freeze the whole unbaked casserole — the texture of the croissants suffers more when they freeze raw in the custard.

This is genuinely one of the recipes I come back to most. It's not complicated, it's not trying to be anything fancy — it's just a really good, satisfying brunch dish that makes mornings easier. I've made it for Eid, for Christmas morning, for a neighbor's get-together, and for random Sunday mornings when I just didn't want to think too hard about breakfast.

The make-ahead piece is what keeps me coming back to it. I can be done with prep by 10pm the night before and spend the next morning actually being present instead of scrambling at the stove. If you're looking for another brunch dish that works the same way, my Berry French Toast Casserole follows the exact same logic — assemble ahead, bake fresh, feed a crowd.

If you make this, I hope your kitchen smells as good as mine does when it comes out of the oven. That buttery, cheesy, eggy smell right at the 35-minute mark is one of my favorite things about Saturday mornings. 🥚🧀✨

If you liked this, you might also like these:

• Berry French Toast Casserole (The Best Make-Ahead Brunch Recipe)
• Provolone Goodness
• One-Pan Creamy Parmesan Chicken and Rice