Hearty Sausage Breakfast Casserole

There's something about a crowded kitchen on a lazy Sunday morning that makes you want to feed everyone in it. My neighbor dropped by unannounced with her kids, and I had eggs, some sausage, and day-old bread sitting around—so I threw together this breakfast casserole without much of a plan. It came out golden and bubbling, and watching their faces light up when they bit into those cheesy, sausage-filled bites made me realize this dish had become my go-to answer for "what's for breakfast?"

I made this for my book club once, and someone actually asked for the recipe before they'd finished their first plate—which, let me tell you, doesn't happen often with my cooking. The house smelled incredible while it baked, and honestly, that aroma alone might be the secret ingredient.

Ingredients

• Breakfast sausage (1 pound): Remove it from the casings and crumble it as it cooks; this lets it brown better and distribute throughout the dish.
• Yellow onion (1 small, finely chopped): Optional, but it adds sweetness and depth—I always use it even though the recipe says you don't have to.
• Red bell pepper (1/2, diced): Brings color and a gentle sweetness that balances the savory sausage beautifully.
• Large eggs (8): They're the binder and the soul of this casserole—don't skimp on quality.
• Whole milk (2 cups): The custard won't be creamy without enough liquid, so measure carefully.
• Shredded cheddar cheese (2 cups): Sharp cheddar gives more flavor than mild; I learned this the hard way after a bland first attempt.
• Shredded mozzarella cheese (1/2 cup): It adds a stretchy, melty quality that cheddar alone can't provide.
• Day-old bread (6 cups, cut into 1-inch cubes): Stale bread absorbs the egg mixture better than fresh—this is non-negotiable.
• Salt, black pepper, mustard powder, and paprika: These seasonings wake up all the flavors without overpowering the dish.

Instructions

Set up and preheat:

Heat your oven to 350°F and grease a 9x13-inch baking dish generously with butter or spray so nothing sticks.

Cook the sausage:

Brown the sausage in a large skillet over medium heat, breaking it apart as it cooks until there's no pink left, about 5-7 minutes. Add the onion and bell pepper if using, and let them soften for another few minutes, then drain off any excess fat.

Layer the bread:

Spread your bread cubes across the baking dish in an even layer, then scatter the cooked sausage and vegetables over the top.

Make the custard:

Whisk together eggs, milk, salt, pepper, mustard powder, and paprika in a large bowl until smooth and well combined.

Add the cheese:

Stir 1 1/2 cups of cheddar and all the mozzarella into the egg mixture so it's evenly distributed.

Combine everything:

Pour the egg and cheese mixture slowly over the bread and sausage, then gently press the bread down with the back of a spatula so it absorbs all that lovely custard.

Top and bake covered:

Sprinkle the remaining cheddar on top, cover the dish with foil, and bake for 30 minutes.

Finish uncovered:

Remove the foil and bake another 15 minutes until the top is golden and the center feels set when you gently jiggle the pan.

Rest before serving:

Let it sit for 10 minutes after it comes out of the oven—this helps it set up and makes slicing easier.

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The moment I realized this dish was special was when my sister asked me to make it for her daughter's baptism brunch. Feeding thirty people from one baking dish felt impossible, but watching families gather around it like it was the main event told me everything.

Make-Ahead Magic

This casserole is one of those rare dishes that actually tastes better when you plan ahead. Assemble it completely the night before, cover it tightly, and refrigerate—the bread will continue soaking up all those eggy flavors overnight, and you'll wake up to a dish that's practically done for you. Just add 10 minutes to the baking time if you're pulling it straight from the fridge, and everything will come out perfect.

Flavor Variations Worth Trying

I've experimented with swapping out cheddar for sharp Swiss cheese, which gives it a more sophisticated edge, or using pepper jack if I'm feeling bold. Adding a handful of sautéed mushrooms or fresh spinach in with the sausage layer turns it into something that feels a little fancier without adding much effort. Some mornings I'll stir a splash of hot sauce into the egg mixture or serve it on the side, and that little kick changes everything.

Serving and Storage Ideas

Serve this warm from the oven with a simple side salad or fresh fruit, though honestly, it's hearty enough to stand on its own. Leftover casserole keeps in the fridge for three days and reheats beautifully in a 300°F oven for about 15 minutes, so it's perfect for those mornings when you want breakfast without lifting a finger.

• Pair it with fresh salsa or hot sauce for an unexpected kick that cuts through the richness.
• A simple green salad on the side balances the dish without stealing the show.
• Save the leftovers—they're just as good cold as they are warm, and they make for stellar midnight snacks.

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This casserole has become my answer to almost every breakfast question, and I think it's because it feels like you've cooked all morning when really you've barely done anything. Make this for people you love, and watch it become their answer too.

Recipe Questions & Answers

→ Can I prepare this dish ahead of time?

Yes, assemble the layers the night before, cover, and refrigerate. Bake as directed, adding 10 minutes if baking straight from the fridge for even warmth.

→ What cheese substitutes work well here?

Swiss or pepper jack cheeses provide tasty alternatives, lending different flavor profiles while maintaining meltiness.

→ How do vegetables enhance this dish?

Chopped onions and bell peppers add sweetness and depth. Additional veggies like spinach or sautéed mushrooms introduce freshness and texture.

→ What type of bread is best for this casserole?

Day-old bread such as French or sourdough with a sturdy crumb absorbs the egg mixture well without becoming soggy.

→ How do I ensure the casserole sets properly?

Bake covered for 30 minutes to cook through, then uncovered for 15 minutes to develop a golden crust and firm center.

→ Can I adjust seasoning for dietary needs?

Absolutely; salt, pepper, paprika, and mustard powder can be customized to taste or omitted based on preferences.