High-Protein Sausage & Hashbrown Breakfast Casserole

Prep Time: 20 minutes
Cook Time: 55 minutes
Total Time: 1 hour 15 minutes
Servings: 8 servings
Calories: 490 kcal per serving

Why You’ll Love This Recipe

This isn’t just any breakfast casserole. Here’s why it’s a staple in our home:

Incredibly Satisfying: With over 30 grams of protein per serving, this casserole provides lasting energy and prevents those mid-morning hunger pangs. It’s a powerhouse meal that fuels your day.
Make-Ahead Magic: Assemble it the night before, pop it in the fridge, and simply bake it in the morning. It’s the secret to a stress-free, impressive breakfast without any early morning chaos.
Totally Customizable: This recipe is a perfect base. Feel free to swap the sausage for bacon or ham, add your favorite veggies like bell peppers or spinach, or switch up the cheese.
Perfect for a Crowd: Easily doubled and baked in a 9×13-inch dish, this recipe serves 8 generously. It’s the ideal dish for feeding a hungry family or a group of weekend guests.
Gluten-Free Goodness: Made with frozen shredded hashbrowns, this casserole is naturally gluten-free, so everyone can enjoy a slice.

🥘 Ingredients

Here’s everything you’ll need to create this delicious casserole.

1 tablespoon olive oil or avocado oil
1 lb ground pork breakfast sausage (mild, spicy, or maple – your choice!)
1/2 cup diced yellow or white onion (about 1/2 a medium onion)
20 oz (about 4 cups) frozen shredded hashbrowns, thawed
12 large eggs
1 cup whole milk or 2% milk
1 teaspoon garlic powder
1 teaspoon onion powder
1/2 teaspoon smoked paprika
1/2 teaspoon salt
1/4 teaspoon black pepper
2 cups shredded sharp cheddar cheese, divided

For Serving (Optional but Recommended):

Fresh chives or green onions, chopped
Salsa or hot sauce
Sour cream or Greek yogurt
Diced avocado

📋 Instructions

Follow these simple steps for a perfect casserole every time.

Part 1: Prep and Cook (About 20 minutes)

Preheat & Prep: Preheat your oven to 375°F (190°C) . Grease a standard 9×13-inch baking dish with non-stick cooking spray or a little butter.
Cook the Sausage and Onion: Heat the olive oil in a large skillet over medium-high heat. Add the ground sausage and diced onion. Cook, breaking the sausage up with a spoon, until the sausage is browned and cooked through and the onion is softened, about 8-10 minutes.
Drain Fat: Carefully drain off any excess grease from the skillet. Set the sausage mixture aside to cool slightly while you prepare the other ingredients.
- Cook’s Tip: Draining the fat is crucial to prevent the casserole from becoming greasy.

Part 2: Assemble the Casserole (About 5 minutes)

Thaw and Press Hashbrowns: Ensure your frozen hashbrowns are fully thawed. For the best texture, place the thawed hashbrowns in a clean kitchen towel or a few layers of paper towels and squeeze firmly to remove as much excess moisture as possible. This helps them get a little crispy on the edges instead of steaming.
Layer the Base: Spread the pressed hashbrowns evenly in the bottom of your prepared baking dish.
Add the Sausage: Sprinkle the cooked sausage and onion mixture evenly over the hashbrown layer.
First Layer of Cheese: Sprinkle 1 cup of the shredded cheddar cheese over the sausage.

Part 3: The Egg Mixture

Whisk the Eggs and Milk: In a large bowl, crack the 12 eggs. Add the milk, garlic powder, onion powder, smoked paprika, salt, and pepper.
Whisk Thoroughly: Whisk vigorously until the eggs are completely broken up and the mixture is smooth and uniform in color. This ensures every bite is perfectly seasoned.

Part 4: Final Assembly and Bake

Pour and Top: Slowly and evenly pour the egg mixture over the entire casserole, making sure to saturate all the layers. Gently shake the dish a little to help the eggs settle. Sprinkle the remaining 1 cup of cheddar cheese on top.
Bake: Place the casserole in the preheated oven and bake for 45-55 minutes.
Check for Doneness: The casserole is done when the center is set and no longer jiggly. A knife inserted into the center should come out clean. The top should be beautifully golden brown and puffy.
Rest: Remove from the oven and let it rest for at least 10-15 minutes before slicing and serving. This resting period is essential; it allows the casserole to set up firmly so you can get clean slices.

✨ Recipe Tips & Tricks

Thaw Your Hashbrowns! This is the #1 tip. Using frozen hashbrowns straight from the bag will add too much water to the casserole, resulting in a soggy texture. Thawing and pressing them dry makes all the difference.
Make-Ahead Instructions: To prepare this casserole the night before, follow the instructions through Step 10 (pouring the eggs and topping with cheese). Cover the dish tightly with plastic wrap or aluminum foil and refrigerate for up to 12 hours. The next morning, remove it from the fridge while the oven preheats. You may need to add 10-15 minutes to the baking time since you’re starting from a cold dish.
Don’t Over-Bake: Over-baking can lead to a dry, rubbery casserole. Start checking for doneness around the 45-minute mark. The edges will be puffed and golden, and the center should be just set.
Let it Rest: We cannot stress this enough! Letting the casserole rest is key for perfect slices. If you cut into it immediately, it will be runny.

🔄 Variations & Substitutions

Meat: Swap the pork sausage for spicy Italian sausage, breakfast turkey or chicken sausage, or cooked and crumbled bacon or diced ham.
Vegetables: Sauté 1 cup of diced bell peppers, mushrooms, or zucchini along with the onion. You can also add a couple of handfuls of fresh spinach to the skillet at the end and let it wilt.
Cheese: Sharp cheddar is classic, but this is also delicious with Monterey Jack, Colby, pepper jack for heat, or a Mexican blend.
Dairy-Free: Use a plant-based sausage, dairy-free milk (like unsweetened almond or oat milk), and your favorite shredded dairy-free cheese alternative.
Add Some Heat: Add a drained can of diced green chiles with the sausage, or sprinkle in some red pepper flakes with the other spices.

❄️ Storage & Reheating

Storage: Store any leftover casserole in an airtight container in the refrigerator for up to 4 days.
Reheating: The best way to reheat is in a skillet over medium heat for a few minutes per side to re-crisp the edges. You can also use the microwave for a quick option (about 60-90 seconds per slice) or reheat in a 350°F oven until warmed through.
Freezing: This casserole freezes beautifully! Wrap individual slices or the whole cooled casserole tightly in plastic wrap, then a layer of aluminum foil. Freeze for up to 3 months. Thaw overnight in the refrigerator before reheating.

🥗 Nutrition Information

Nutrition information provided is an estimate and will vary based on the specific ingredients and brands used. This information is for one serving based on the recipe yielding 8 servings.

Calories: 490 kcal
Carbohydrates: 17g
Protein: 31g
Fat: 33g
Saturated Fat: 13g
Cholesterol: 335mg
Sodium: 910mg
Fiber: 1g
Sugar: 3g