Name: Overnight Sausage Egg Casserole Recipe
Prep time: 20 min
Cook time: 45 min
Total time: 1 h 5 min
Cuisine: American
Ingredients: 10 to 12 ounces sausage (casing removed); 2 cloves garlic (minced); 3 cups fresh spinach (90g); 2 large bell peppers (diced); ½ medium yellow onion (diced); Salt and pepper (to taste); 12 large eggs; ½ cup milk (any) (120g); ½ cup shredded cheese (any flavor; divided) (56g); Olive oil

There’s something truly comforting about a warm, homey breakfast that welcomes you in the morning. This Overnight Sausage Egg Casserole Recipe is exactly that—a hearty, flavorful dish that you prepare ahead, then just pop in the oven when you’re ready. Trust me, it makes busy mornings feel a little less hectic and a whole lot tastier.

The image shows a glass baking dish with six square pieces of a baked egg dish. Each piece has multiple layers: a golden, slightly browned cheese topping with melted, textured surface, speckled with dark green spinach patches and small red pepper bits. Below the cheese layer, you can see a creamy, slightly crumbly egg mixture with visible red and green vegetable pieces, and a light base of what seems to be cooked mushrooms at the bottom. One square piece is being lifted gently by a silver spatula over a white marbled surface. The whole dish looks warm and appetizing. photo taken with an iphone --ar 2:3 --v 7

Jump to:

Why You'll Love This Recipe
Ingredients & Why They Work
Make It Your Way
Step-by-Step: How I Make Overnight Sausage Egg Casserole Recipe
Top Tip
How to Serve Overnight Sausage Egg Casserole Recipe
Make Ahead and Storage
Frequently Asked Questions:
Final Thoughts
Overnight Sausage Egg Casserole Recipe

Why You'll Love This Recipe

I’m genuinely excited to share this Overnight Sausage Egg Casserole Recipe because it’s both adaptable and genuinely delicious—a true lifesaver when you want a fuss-free, crowd-pleasing breakfast or brunch.

Make ahead magic: Prep it the night before and wake up to a nearly ready breakfast, which is a game changer for busy schedules.
Loaded with flavor: Sautéed sausage, fresh vegetables, and melty cheese combine so beautifully every single time.
Flexible ingredients: You can easily swap veggies and cheese to suit whatever you have on hand or your personal taste.
Feeds a crowd: Perfect for family breakfasts or brunch gatherings—you’ll get plenty of compliments (and second helpings!).

The image shows a close-up of a thick square slice of a baked egg dish on a white plate with a speckled pattern, resting on a white marbled surface with a green cloth nearby. The dish has about three layers: the top layer is a melted golden and light orange cheese with some darker browned spots, the middle layer is creamy and filled with small bits of green leafy vegetables and red pieces, and the bottom layer is firm and slightly textured. Behind the egg dish, there are roasted potato chunks with a crispy-looking golden brown surface. A silver fork lies beside the egg slice, partially resting on the plate. Photo taken with an iphone --ar 2:3 --v 7

Ingredients & Why They Work

When I first started making this casserole, I loved how these simple ingredients come together in such a satisfying way. Each element plays a role to create a balanced, hearty dish with fresh veggies, rich eggs, and savory sausage.

Flat lay of a mound of raw fresh sausage meat, two peeled garlic cloves, a handful of fresh vibrant green spinach leaves, two large diced red and yellow bell peppers, half a medium yellow onion diced, twelve whole brown eggs with clean shells, a small white ceramic bowl of golden olive oil, a small white ceramic bowl of fresh milk, a small white ceramic bowl filled with shredded pale yellow cheese, coarse salt and black peppercorns scattered neatly in white ceramic dishes, all arranged symmetrically on a clean white marble surface, soft natural light, photo taken with an iPhone, professional food photography style, fresh ingredients, white ceramic bowls, no bottles, no duplicates, no utensils, no packaging --ar 2:3 --v 7 --p m7354615311229779997

Sausage: I prefer Italian sausage for a bit of spice, but mild works just as well. Removing casing makes browning easier.
Olive oil: Used just a little to sauté veggies, adding subtle richness without overpowering.
Garlic: Fresh minced garlic gives a warm, aromatic base to the veggies.
Spinach: Adds freshness and a pop of color while keeping things light.
Bell peppers: I use red and yellow for sweetness and crispness; plus, they brighten up the dish.
Yellow onion: Provides a mild, sweet base that softens beautifully when cooked.
Salt and pepper: Essential for seasoning as you go to keep layers of flavor balanced.
Eggs: The star ingredient that binds everything together—don’t skimp here!
Milk: Adds creaminess to the eggs; any kind works depending on your preference.
Shredded cheese: I usually go for cheddar or a blend, but feel free to experiment; it melts perfectly into the casserole.

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Note: You'll find the complete list of ingredients, along with their exact measurements, in the printable recipe card at the bottom of this post.

Make It Your Way

One of the best things about this Overnight Sausage Egg Casserole Recipe is how easy it is to personalize. I often swap veggies or cheese based on what's in my fridge, and you can too—don’t be shy about making it your own!

Variation: I once added mushrooms and swapped sausage for turkey sausage, which lightened things up while keeping all the flavor.
Spinach sub: Kale or chard work beautifully if you want a heartier green.
Cheese swaps: Pepper jack adds a nice kick if you’re feeling adventurous.
Make it vegetarian: Simply omit the sausage and add more veggies and your favorite plant-based sausage alternative.

Step-by-Step: How I Make Overnight Sausage Egg Casserole Recipe

Step 1: Brown the Sausage Perfectly

Start by removing the casing from your sausage and browning it gently in a large skillet over medium heat. I like to break it up into small crumbles as it cooks, which helps it distribute evenly through the casserole. Even if your sausage is pre-cooked, I recommend a quick browning to deepen the flavor and get a little crispy texture—that’s my secret step!

Step 2: Sauté Your Veggies to Tender Perfection

Using the same skillet, add a splash of olive oil if needed. Toss in minced garlic, fresh spinach, diced bell peppers, and onion. Cook until the vegetables soften and the spinach wilts—about 6 to 7 minutes. Don’t forget to season with salt and pepper near the end to bring out all those lovely flavors.

Step 3: Layer and Mix

Transfer the browned sausage to your prepared casserole dish, then add the sautéed vegetables on top. I usually give it a gentle stir here, just to combine everything evenly without mushing it up.

Step 4: Whisk and Pour the Egg Mixture

In a separate bowl, whisk together your eggs, milk, and half of your shredded cheese until fully blended. Pour this mixture evenly over the sausage and veggies in the dish, then sprinkle the remaining cheese on top along with a bit more salt and pepper.

Step 5: Chill or Bake

This casserole is very forgiving—if you want to bake it right away, pop it in a 375ºF (191ºC) oven for about 45 minutes until the edges are golden brown. Otherwise, cover it with foil or plastic wrap and refrigerate for up to 24 hours. This makes it an excellent overnight prep option, freeing up your morning.

Step 6: Let it Rest and Serve

When it’s done baking, allow the casserole to cool for at least 15 minutes before slicing. This resting time helps it set so your slices hold shape—plus, it’s easier to serve and enjoy without making a mess!

Top Tip

Having made this casserole numerous times, I've picked up a few tricks that really elevate the final dish and avoid common pitfalls. These will help you make your Overnight Sausage Egg Casserole Recipe impressively every time.

Don’t overbake: Keep an eye on the edges; once they brown and the center feels set but not dry, it’s time to pull it out.
Season the layers: Season your veggies and sausage well individually so the casserole never tastes bland.
Use a glass or ceramic dish: These materials promote even cooking and browning better than metal pans.
Cool before slicing: It’s tempting to dig in right away, but waiting helps hold the casserole’s shape much better.

How to Serve Overnight Sausage Egg Casserole Recipe

overnight sausage casserole - Serving Suggestion

Garnishes

I love topping mine with a little fresh parsley or chopped chives to add brightness and a pop of color. Sometimes, a dollop of salsa or a spoonful of avocado on the side works wonders too—adds some fresh zest and creaminess that complements the casserole perfectly.

Side Dishes

This casserole pairs beautifully with fresh fruit salad or a simple green salad for a lighter contrast. If you want something heartier, crusty bread or soft dinner rolls are fantastic for soaking up any leftover eggy goodness.

Creative Ways to Present

For special occasions, I’ve served this casserole in individual ramekins—so each guest gets a perfectly portioned personal casserole. Another fun idea is layering in a glass dish so guests can admire those colorful veggies and sausage layers before digging in!

Make Ahead and Storage

Storing Leftovers

After baking, I usually wrap the casserole tightly with foil and store it in the fridge. It stays delicious for up to 5 days—perfect for quick breakfasts throughout the week.

Freezing

I’ve had great success freezing the casserole both before and after baking. If freezing unbaked, just cover super tightly with plastic wrap and foil to avoid freezer burn. Thaw overnight in the fridge before baking. Frozen leftovers reheat wonderfully, too.

Reheating

When reheating individual portions, I pop them in the microwave for about 1 to 2 minutes on medium power. For a whole casserole, cover loosely with foil and bake at 350ºF (177ºC) until warmed through—usually around 20 minutes works well.

Frequently Asked Questions:

Can I use turkey or chicken sausage instead of pork sausage?

Absolutely! Turkey or chicken sausage makes a great leaner alternative and works perfectly in this casserole. Just cook it the same way as you would pork sausage for best flavor.

How long can I refrigerate the casserole before baking?

You can safely prepare and refrigerate this casserole for up to 24 hours before baking. This makes it ideal for overnight prep and reduces morning stress.

Can I make this recipe vegetarian?

Yes! Simply skip the sausage and add extra vegetables or a vegetarian sausage substitute. Consider adding mushrooms, zucchini, or even some cooked beans for texture and protein.

What’s the best way to freeze this casserole?

For freezing, cover the entire unbaked casserole tightly with plastic wrap and then foil to prevent freezer burn. When ready, thaw overnight in the fridge, remove plastic wrap, and bake as usual. It freezes well after baking too—just reheat gently.

Final Thoughts

This Overnight Sausage Egg Casserole Recipe has become one of my go-to favorites because it’s reliable, easy, and so full of comforting flavors. I love starting my day knowing I get to enjoy a warm dish that I spent just a little bit of time preparing ahead. You’re going to appreciate how this recipe simplifies mornings while still tasting like you made something special. Give it a try—you might just find yourself making it over and over, like I do!