Cheesy Low Carb Breakfast Casserole with Sausage and Spinach

This low carb breakfast casserole is the answer when you want a hot, filling breakfast without the carb crash. Sausage, spinach, and a whole lot of cheese bake into one pan that you can prep the night before and slide into the oven in the morning.

It’s sturdy enough to hold up all week, so make it on Sunday and you’ve got breakfast sorted for days. No flour, no bread, just the good stuff.

Why This Casserole Stays on Repeat

The edges puff up golden while the center stays creamy and custardy. Every slice is packed with savory sausage crumbles and ribbons of tender spinach.

I keep coming back to this one because the heavy cream does the heavy lifting. It gives the eggs a silky texture that reheats well, so leftovers actually taste just as good on Wednesday as they did right out of the oven.

Ingredients

• 1 lb breakfast sausage: turkey, or chicken all work fine
• 1 tbsp olive oil: only if your sausage is lean and sticks
• 1 small onion: diced, about 3/4 cup
• 1 red bell pepper: diced, for a little sweetness and color
• 3 cloves garlic: minced, fresh works best here
• 5 oz fresh baby spinach: a full 5-oz clamshell or bag
• 12 large eggs: the foundation of the whole dish
• 1/2 cup heavy cream: for that custardy bite
• 2 cups shredded cheddar cheese: sharp cheddar gives the most flavor, divided
• 1/2 tsp fine sea salt
• 1/4 tsp black pepper
• 1/4 tsp crushed red pepper flakes: optional, for a tiny kick of heat
• Butter: for greasing the baking dish

Variations and Swaps

• Protein Swap: Use hot Italian sausage or chorizo for more heat.
• Leafy Greens: Swap spinach for chopped kale or Swiss chard; just sauté them a minute or two longer until tender.
• Dairy-Free Option: Sub the heavy cream with full-fat canned coconut cream and use a good melting dairy-free cheddar.
• Extra Veggies: Sauté mushrooms or zucchini first until their liquid cooks off so the casserole doesn’t get watery.
• Milder Cheese: Monterey Jack or a Mexican blend mellows things out.

If this hits the spot, you’ll probably like my Zucchini and Bacon Frittata too.

How to Make Low Carb Breakfast Casserole

Step 1: Brown the Sausage and Vegetables

Preheat your oven to 350°F (175°C) and grease a 9×13 inch baking dish with butter. In a large skillet over medium-high heat, cook the 1 lb sausage, breaking it into small crumbles, until no longer pink, about 6 to 8 minutes. Add the diced onion and bell pepper and cook, stirring often, until softened, about 4 minutes. Stir in the 3 cloves minced garlic and cook for 30 seconds, then add the 5 oz spinach and cook until completely wilted and the pan is dry, about 2 minutes.

The sausage will be golden at the edges and the spinach will shrink to a dark tangle. The pan should smell richly savory, with no raw garlic bite left.

Step 2: Whisk the Eggs and Cream

While the sausage mixture cools slightly, crack the 12 eggs into a large bowl. Add the 1/2 cup heavy cream, 1/2 tsp salt, 1/4 tsp pepper, and the red pepper flakes if you’re using them. Whisk steadily until the yolks and whites are fully blended and the mixture looks pale and a little frothy, about 30 seconds.

The cream gives the eggs a custardy finish instead of a spongy one. The whisked mixture should smell faintly of cream with no streaks of yolk.

Step 3: Assemble the Casserole

Spread the cooked sausage and vegetables evenly across the bottom of the greased dish. Sprinkle on half of the 2 cups shredded cheese, then pour the egg mixture over everything. Tilt the dish gently so the eggs settle into all the gaps and the depth is even. Top with the remaining cheese.

At this stage, you can cover and refrigerate the assembled dish for at least 2 hours or up to 12 hours if you’re making it ahead. That overnight rest actually lets the flavors marry a little deeper.

Step 4: Bake Until Set

Bake the casserole until the center is just set with a slight jiggle and the edges are puffed and deeply golden, about 35 to 40 minutes. A knife inserted near the middle should come out clean.

The cheese on top will be melted and bubbly with browned spots. If you press lightly in the center, the surface springs back instead of feeling liquid underneath.

Step 5: Slice and Serve Warm

Let the casserole rest for 5 minutes so the squares hold their shape. Cut into 8 pieces and use a wide spatula to lift them out.

The slices should be tall and sturdy, with ribbons of spinach and sausage throughout. The cheese pulls into little strings when you lift a piece.

A Few Notes Before You Start

• Heavy cream is what keeps the texture creamy rather than rubbery — half-and-half works in a pinch but the result will be a bit looser.
• A glass baking dish cooks more gently and prevents the edges from browning too fast. Metal works fine, just check 5 minutes early.
• This freezes well: cool completely, slice, wrap individual squares tightly, and freeze for up to 3 months. Thaw overnight in the fridge and reheat gently.

Bake times by pan size:

Storing Leftovers

Refrigerate leftover squares in an airtight container for up to 4 days. Reheat individual portions in the microwave for 1 to 2 minutes or in a 300°F (150°C) oven for about 10 minutes. For longer storage, wrap and freeze as noted above.

What to Serve With This Casserole

This dish is a full meal on its own, but if you’re serving it for brunch, a simple green salad with a lemon vinaigrette cuts through the richness nicely. Roasted cherry tomatoes or a few slices of avocado on the side add a fresh note without any extra carbs.

Frequently Asked Questions

Can I make this dairy-free?

Yes. Swap the heavy cream for full-fat canned coconut cream and use a good dairy-free shredded cheddar that melts well. The texture will be close to the original.

Can I use frozen spinach instead of fresh?

Definitely. Thaw 10 oz of frozen spinach and squeeze out every last drop of water before adding it to the skillet. Any extra moisture will make the casserole soggy.

Is this recipe keto-friendly?

Yes. With about 4 g net carbs per serving, it fits easily into a keto meal plan. Double-check your sausage for added sugars or fillers.

Can I lighten it up a little?

You can use turkey sausage and half-and-half instead of heavy cream, though the texture won’t be quite as rich. Reduced-fat cheese also works but melts a little differently.

Cheesy Low Carb Breakfast Casserole Recipe

Print Recipe Pin Recipe

Prep Time 15 minutes mins

Cook Time 35 minutes mins

Total Time 50 minutes mins

Servings: 8 servings

Calories: 405

Ingredients Method Notes

Ingredients

  

• 1 lb breakfast sausage
• 1 tbsp olive oil (if needed)
• 1 small onion, diced
• 1 red bell pepper, diced
• 3 cloves garlic, minced
• 5 oz fresh baby spinach
• 12 large eggs
• 1/2 cup heavy cream
• 2 cups shredded cheddar cheese, divided
• 1/2 tsp fine sea salt
• 1/4 tsp black pepper
• 1/4 tsp crushed red pepper flakes (optional)
• Butter for greasing

Method

 

1. Preheat oven to 350°F (175°C) and butter a 9×13 inch baking dish. In a skillet over medium-high, cook sausage 6-8 minutes until browned. Add onion and pepper, cook 4 minutes. Add garlic and spinach and cook until wilted and dry, 2 minutes.
2. Whisk eggs, heavy cream, salt, pepper, and red pepper flakes in a large bowl until pale and frothy, about 30 seconds.
3. Spread sausage mixture in the dish, top with half the cheese, pour eggs over everything, then sprinkle remaining cheese on top.
4. Bake until center is set with a slight jiggle and edges are golden, 35-40 minutes. A knife inserted near the center should come out clean.
5. Let rest 5 minutes, then slice into 8 squares and serve warm.

Notes

If assembling ahead, cover and refrigerate up to 12 hours. Add 5-10 minutes to the bake time when going straight from the fridge. The casserole will puff up significantly in the oven and settle slightly as it rests.