Make-Ahead Breakfast Casserole With Sausage and Peppers

A make-ahead breakfast casserole earns its place on the mornings you don’t want to be cracking eggs while a houseful of guests waits for coffee. I put this one together the night before, cover it, and let the oven do the work while everyone wanders in.

I cook the sausage, peppers, and onion down first, every time, because raw peppers release water into the eggs and can leave the center soggy. One pound of sausage stretches across six servings, enough to feed a crowd without cooking a second pan.

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Why You’ll Love This Recipe

• The morning stays hands-off: the work happens the night before, and all that’s left at breakfast is turning on the oven.
• It feeds 6 from a single pound of sausage, because the eggs, peppers, and two cheeses do most of the carrying.
• It’s a savory, herb-flecked breakfast: Gruyère and cheddar melt through the eggs, with chives and parsley scattered over the top.
• You need one skillet and one baking dish, and nothing on the list is a specialty ingredient.
• Leftovers keep for days and freeze well, so a single bake covers weekday breakfasts too.

Ingredients You’ll Need

Here’s what’s worth noting before you start; the printable card below has the full list with quantities.

• Pork sausage: brown it well until it takes on real color, since that browning is most of the savory flavor in the finished dish. One pound is the backbone here.
• Red and green bell peppers: using both keeps the casserole colorful and a little sweet. Dice them small so they soften through in the few minutes they get in the pan.
• Gruyere cheese: it melts smoothly and brings a nutty depth that cheddar alone won’t give you. It’s also the one splurge on the list, so it’s the first place to economize if you need to (see the variations below).
• Cheddar cheese: half goes into the egg mixture and half on top, which gives you a browned, bubbling lid over a creamy inside.
• Eggs: let them sit out for about 10 minutes first. Room-temperature eggs blend more smoothly into the sausage and cheese, and six of them bind the whole casserole.
• Chives and parsley: stirred in and scattered over at the end, they keep the dish from tasting heavy and give it a fresh, green finish.

How to Make Breakfast Casserole

Scroll down for the full recipe instructions card containing a full printable recipe and measurements in both US customary and metric units.

Brown the sausage

Place a non-stick skillet over medium-high heat and add the pork sausage, breaking it apart as it cooks until browned.

I pour off most of the rendered fat after cooking so it does not pool in the finished dish.

Cook the vegetables

Stir in the onion, both bell peppers, the garlic, and a little salt and pepper. Give them 7 to 10 minutes, until they’re soft rather than just wilted.

Softening them fully now is what lets the center set cleanly later, so don’t rush it.

Combine the mixture

In a large bowl, mix the cooked sausage and vegetables with the Gruyère, half of the cheddar, and the eggs until everything is well combined.

Assemble

Grease a casserole dish, pour in the mixture, and spread it out evenly. Scatter the remaining cheddar over the top.

Bake

Bake at 350°F (180°C) for about 20 minutes, until it’s hot and bubbling and the center reaches 160°F (71°C).

If you assembled it the night before and it’s been in the fridge, give it a little longer and check the internal temperature rather than going by the clock.

Garnish and serve

Scatter the chives and parsley over the top just before serving.

Recipe Notes and Expert Tips

• Go by temperature, not the timer. The casserole is done when the center hits 160°F (71°C), and a dish that starts out fridge-cold will need a few extra minutes.
• Grease the dish more than feels necessary. That’s what lets the first square lift out in one piece instead of sticking to the bottom.
• Let it sit for a few minutes after cooking before slicing. The set firms up as it rests, and the slices hold their shape.

Recipe Variations

• If Gruyère isn’t in the budget this week, use all cheddar instead. It works because you’re swapping one cheese for another, so the bake time and the rest of the recipe stay the same.
• Fold a handful of chopped spinach in with the peppers, but cook it down first. That works because dry spinach won’t weep water into the eggs the way raw leaves would.
• Using turkey sausage instead of pork makes the dish lighter. It browns faster and can lose moisture more quickly. I haven’t tested it in this casserole, so use the timing as a starting point.

How to Store Leftovers

If making it ahead, assemble the dish completely, cover it tightly, and refrigerate it. Bake within 24 hours.

This is a raw egg mixture held cold, not a cooked leftover, and after a day, the texture starts to suffer.

Once baked, let the casserole cool completely, then cover it tightly or portion it into airtight containers.

Don’t leave the casserole out at room temperature for more than 2 hours, or more than 1 hour if the kitchen is above 90°F (32°C).

What to Serve With Breakfast Casserole

This is a rich, savory plate, so I build the rest of the table around it lightly. Warm cheddar biscuits are the one bread I’ll add, since they pull double duty for anyone mopping up a plate.

For a brunch spread where people want something sweet alongside the eggs, a tray of sheet pan pancakes cooks at the same time and cuts into squares, so you’re not standing at the stove flipping while the casserole rests.

FAQs

More Casseroles to Try

If you like this one, here’s where I’d go next:

•  Chicken Casserole for a fast weeknight, since the shredded chicken and noodles come together in about 25 minutes.
• Cowboy Casserole for a hearty family dinner, since taco-seasoned beef and corn hide under a crispy tater-tot lid.
• Chili Relleno Casserole for Mexican-style heat without deep-frying, since roasted peppers and Monterey Jack bake together instead of frying.
• Tuna Casserole is the pantry night, built on canned tuna and noodles with no fresh meat to buy.