Overnight Egg Casserole (Sausage, Egg, and Cheese)

Why This Is The Best Overnight Breakfast Casserole

When it comes to breakfast casseroles, it doesn't get much better than this make-ahead egg bake. It has the perfect combination of flavors, and it's made with simple breakfast ingredients like eggs, cheddar cheese, sausage, and bread.

The end result is a savory, cheesy, hearty egg breakfast casserole your family won't be able to get enough of! At least mine can't. Plus, it's endlessly customizable, too, so you can make this casserole again and again without ever getting bored.

The results are seriously out-of-this-world delicious for how easy this recipe is. In fact, everything comes together the night before, so all you have to do is grab it out of the fridge and put it in the oven for the perfect make-ahead breakfast. Check out what this reader said about this overnight breakfast casserole:

Very easy whip up the night before. I popped it in the oven Sunday morning for a family breakfast and my family loved it! -Kayla Smart

By the way, since the oven does most of the heavy lifting, you'll have plenty of time to work on some breakfast sides like this million dollar bacon and these air fryer hash browns.

Ingredients for Overnight Egg Casserole

• 1lb. mild sausage, removed from the casing
• 6 medium eggs
• 2 cups milk
• Salt and pepper, to taste
• 1 teaspoon whole-grain mustard
• 1 cup cheddar cheese, shredded
• 6 slices of bread, cubed

Oh, and you can basically use the same ingredients to make this Christmas breakfast casserole, Bisquick breakfast casserole, and breakfast casserole with ham as well. So if you're craving more easy breakfast casseroles, definitely check those out next!

Ingredient Substitutions and Suggestions

You can absolutely make this overnight egg casserole exactly as written, but it's also very flexible if you want to put your own spin on it. Here are some easy ways to switch things up without breaking the recipe.

Sausage swaps:

• You can use almost any breakfast-style sausage you like.
• Try pork breakfast sausage, spicy or mild Italian sausage, or herbed chicken sausage.
• If you are using sausage links, remove the casings so you can crumble the meat as it cooks.

Cheese options:

• Cheddar is classic and melts well, but you can mix and match.
• Mozzarella, Colby Jack, Pepper Jack, or Swiss all work great in this casserole.
• For extra richness, add an extra ½ cup of cheese sprinkled over the top before baking.

Bread choices:

• French bread, sourdough, brioche, challah, or thick-cut sandwich bread all work.
• Day-old or slightly stale bread is best because it soaks up the egg mixture without turning mushy.

Veggies to add more flavor and color:

• Diced red or green bell peppers
• Sliced mushrooms (sauté briefly first to remove excess moisture)
• Green onions or finely chopped regular onions
• Spinach, kale, or broccoli florets (lightly cooked or steamed)

Extra add-ins for a heartier casserole:

• Cooked, crumbled bacon
• Diced ham
• Frozen hash browns or shredded potatoes
• A sprinkle of everything bagel seasoning on top before baking

These tweaks let you use what you already have on hand and help you turn this overnight breakfast casserole into your own signature version while keeping the base method and texture the same.

How To Make Overnight Egg Casserole

Step 1: Cook The Sausage

First, you'll want to coat a 9-inch casserole dish with some butter or nonstick cooking spray. Then, you can take out a large skillet and set it over medium-high heat. Once the pan is hot, add the pork sausage and cook for a few minutes, breaking it apart as it browns and cooks through.

Step 2: Make The Egg Mixture

Up next, grab a large bowl and whisk together the eggs with milk, salt, pepper, and whole-grain mustard. As soon as everything is fully mixed, stir in the shredded cheddar cheese.

Step 3: Assemble The Casserole

Now that the filling is ready, it's time to assemble the casserole. First, place the cubed bread in the prepared baking dish, then add the browned sausage and pour the egg mixture on top. Then transfer the prepared breakfast casserole to the fridge and let it chill overnight. 

Step 4: Bake The Casserole

The next day whenever you're ready to eat this delicious casserole, you'll want to preheat the oven to 350°F (180°C). Then, you can take the casserole out of the fridge while the oven preheats. Once the oven is heated, you can put the casserole in it and let it bake for about 45 minutes. When the time is up, allow the finished casserole to cool for 5 minutes before slicing and serving.

Expert Tips To Make The Best Overnight Egg Casserole

• Use sturdy bread so it holds up overnight. Choose a heartier bread like French bread, sourdough, brioche, or thick-cut sandwich bread. Slightly stale or day-old bread works best because it soaks up the egg mixture without disintegrating. Very soft fresh bread can turn mushy and give the casserole a soggy texture.
• Brown the sausage well and drain the fat. Cook the pork sausage over medium-high heat until it is nicely browned and no pink remains, breaking it into small crumbles as it cooks. Browning deeply adds flavor, and draining off excess grease keeps the casserole from being overly oily and helps the egg mixture set cleanly.
• Season the egg mixture, not just the sausage. Whisk the eggs, milk, salt, pepper, and whole-grain mustard until smooth, then stir in the cheddar cheese. Seasoning the egg mixture ensures every bite of the casserole has flavor, not just the sausage. The mustard adds a subtle tang and depth you will taste in the final dish.
• Layer the bread and sausage evenly. Spread the bread cubes in an even layer in the baking dish, then scatter the browned sausage evenly over the bread. This helps the sausage and cheese distribute throughout the casserole so you do not end up with some pieces that are all bread and others all sausage.
• Make sure everything is soaked before chilling. After you pour the egg mixture over the bread and sausage, gently press the bread down with the back of a spoon or your hands to help it soak up the custard. You want the bread to be mostly submerged. Cover the dish tightly and refrigerate overnight so the bread absorbs the egg mixture fully and bakes up custardy and structured.
• Bring the dish closer to room temperature before baking. When you take the casserole out of the fridge, let it sit on the counter for 15–20 minutes while the oven preheats. Baking a very cold dish straight from the fridge can cause the center to take longer to set and the edges to overbrown. Letting it warm slightly helps it bake more evenly.
• Cover with foil if the top browns too quickly. If you notice the top getting very dark before the center is set, loosely tent the casserole with aluminum foil during the last 10–15 minutes of baking. This prevents overbrowning while the eggs finish cooking in the middle.
• Check for doneness in the center. The casserole is done when the center is set and no longer jiggly, and a knife or toothpick inserted in the middle comes out clean or with only a bit of melted cheese, not wet egg. If the center still looks loose, give it another 5–10 minutes and check again.
• Rest before slicing. Let the casserole cool for at least 5–10 minutes before cutting into it. This short rest allows the eggs to firm up slightly so slices hold together and do not fall apart when you serve them.

Overnight Egg Casserole FAQS

Can I make this overnight egg casserole ahead of time?

Yes, that is exactly how this recipe is designed to be used. Assemble the casserole completely, that would be the bread, sausage, cheese, and egg mixture, cover it tightly, and refrigerate it overnight. The next morning, let it sit at room temperature briefly while the oven preheats, then bake as directed. The overnight soak gives you the best texture and makes breakfast very easy.

What kind of bread works best in this breakfast casserole?

Sturdy bread that can soak up the egg mixture without falling apart is ideal. French bread, sourdough, Italian bread, brioche, or thick-cut white or wheat sandwich bread all work well. Slightly stale bread is actually perfect for this, since it absorbs more custard and holds its shape in the finished casserole.

Can I use a different meat instead of pork sausage?

Yes, you can swap the pork sausage for turkey sausage, chicken sausage, cooked bacon, or diced ham. Just make sure whatever meat you use is fully cooked and drained of excess fat before adding it to the casserole. If you use a milder protein like turkey sausage or ham, you may want to bump up the seasoning slightly in the egg mixture.

Can I add vegetables to the overnight egg casserole?

Absolutely. Vegetables like bell peppers, onions, spinach, mushrooms, or broccoli are great additions. Just sauté them first to remove excess moisture and soften them, then let them cool slightly before adding them to the baking dish along with the sausage. This keeps extra liquid from making the casserole watery.

How do I store leftover breakfast casserole?

Let any leftovers cool to room temperature, then cover the dish or transfer slices to an airtight container. Store in the refrigerator for 3–4 days. This makes it great for meal prep since you can reheat individual portions for easy breakfasts during the week.

How do I reheat leftover egg casserole?

You can reheat individual slices in the microwave for a quick option, but for the best texture, place slices in a baking dish, cover loosely with foil, and warm in a 300°F (150°C) oven until heated through. This keeps the eggs from overcooking and drying out.

Can I freeze overnight egg casserole?

Yes, you can freeze it after baking. Allow the casserole to cool completely, then cut it into portions. Wrap each piece tightly in plastic wrap and place them in a freezer-safe bag or container. Freeze for up to 2–3 months. Thaw overnight in the refrigerator and reheat in the oven or microwave before serving.

Can I make this without letting it sit overnight?

You can bake it right after assembling if you are in a hurry, but the texture will be a bit different. The bread will not have quite as much time to absorb the egg mixture, so the center may be slightly less custardy. If you skip the overnight rest, try to let the assembled casserole sit for at least 30 minutes before baking so the egg can soak in.

Wrapping It Up

Well, that's how to make overnight egg casserole! This easy egg bake is about as quick, easy, and convenient as making breakfast for a big group can be. Plus, it's always a huge hit too.

Anyway, I hope you love this breakfast casserole recipe as much as I/we do. As always, if you give this recipe a try, let us know how it goes in the comments below.

More Casserole Recipes To Try

If you liked this easy breakfast casserole recipe, we have plenty more casseroles on the blog for you to try next!

Check these out:

• Cracker Barrel hashbrown casserole
• Sausage cream cheese casserole
• Mexican breakfast casserole
• Loaded cauliflower casserole
• Mexican casserole
• Chicken divan
• Cheeseburger casserole
• Hashbrown egg casserole

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