Easy Breakfast Casserole with Sausage and Hash Browns (Make Ahead)

This breakfast casserole is the recipe I make every Christmas morning, every time we have house guests, and honestly most Sundays too. It has crispy hash browns, savory sausage, lots of melty cheese and fluffy eggs, all baked together in one dish. The best part is that you can put it together the night before and just slide it into the oven in the morning. While it bakes, I make coffee and actually get to sit down for a minute.

Quick answer: To make a breakfast casserole, brown 1 lb (450g) of breakfast sausage and spread it in a greased 9×13 inch dish with 30 oz (850g) of thawed shredded hash browns and 2 cups (225g) of cheddar. Whisk 10 eggs with 2 cups (480 ml) of milk, salt, pepper and mustard powder, pour it over the top, and bake at 350°F (175°C) for 50 to 60 minutes until the center is set.

It feeds 10 to 12 people, and leftovers reheat really well for busy weekday mornings.

Why You Will Love This Breakfast Casserole

• It feeds a crowd. One 9×13 inch dish gives you 10 to 12 hearty squares.
• You make it the night before. Mix it up in the evening, then bake it in the morning. No early alarm needed.
• It uses simple ingredients. Eggs, milk, sausage, frozen hash browns and cheese. That is basically it.
• It is easy to change. Swap the meat, add vegetables, or make it vegetarian. I share my favorite versions below.
• It reheats well. Leftover squares make a fast weekday breakfast in about a minute.

Ingredients

You will need a 9×13 inch (23×33 cm) baking dish.

• 1 lb (450g) breakfast sausage (pork sausage meat in the UK)
• 30 oz (850g) frozen shredded hash browns, thawed
• 2 cups (225g) shredded sharp cheddar cheese, divided
• ½ cup (75g) diced bell pepper (optional)
• 4 green onions, sliced (optional)
• 10 large eggs
• 2 cups (480 ml) whole milk
• 1 tsp salt
• ½ tsp black pepper
• ½ tsp garlic powder
• 1 tsp dry mustard powder
• Butter or cooking spray for the dish

A few notes on the ingredients

Hash browns: Frozen shredded hash browns are the easiest choice. Thaw them in the fridge overnight, then squeeze out as much water as you can in a clean kitchen towel. This one step keeps the casserole from getting soggy. Frozen diced potatoes (sometimes called Southern style) work too.

Sausage: I use a regular pork breakfast sausage. If you can only find sausages in casings, just slice them open and squeeze out the meat.

Mustard powder: You will not taste mustard, but it makes the cheese and eggs taste richer. If you do not have it, use 1 tsp of regular Dijon mustard.

Milk: Whole milk gives the creamiest texture. You can use half milk and half cream for an extra rich casserole.

How to Make Breakfast Casserole (Step by Step)

1. Prep the dish and oven. Heat your oven to 350°F (175°C). Grease the baking dish well with butter or cooking spray.
2. Brown the sausage. Cook the sausage in a large skillet over medium high heat for 7 to 8 minutes, breaking it into small crumbles. If you are using bell pepper, add it for the last 3 minutes. Drain off the extra grease.
3. Layer the potatoes. Spread the thawed, squeezed hash browns evenly over the bottom of the dish. Season them lightly with a pinch of salt.
4. Add the sausage and cheese. Scatter the sausage over the potatoes, then sprinkle with 1½ cups (170g) of the cheese and the green onions.
5. Mix the eggs. In a large bowl, whisk the eggs, milk, salt, pepper, garlic powder and mustard powder until smooth and well combined.
6. Pour and top. Slowly pour the egg mixture over everything. Gently press down with a spatula so the potatoes soak it up. Sprinkle the rest of the cheese on top.
7. Bake. Bake uncovered for 50 to 60 minutes, until the top is golden and the center is set. A knife in the middle should come out clean, and the eggs should reach 160°F (71°C).
8. Rest and slice. Let it sit for 10 minutes before cutting. This helps it hold together in neat squares.

Step	Time
Prep	20 minutes
Bake	50 to 60 minutes
Rest	10 minutes
Total	About 1 hour 30 minutes

How to Make It the Night Before

This is how I make it for holidays and busy weekends.

1. Follow steps 1 to 6, but do not turn on the oven yet.
2. Cover the dish tightly with foil or plastic wrap (cling film) and put it in the fridge for 8 to 24 hours.
3. In the morning, take it out while the oven heats up, about 20 to 30 minutes. A cold glass dish going straight into a hot oven can crack.
4. Bake as directed, adding 10 to 15 minutes since it starts cold.

The potatoes soak up the eggs overnight, so the make ahead version is actually a little more tender and custardy. Many people in my family like it better this way.

Easy Breakfast Casserole Variations

Once you have made it once, try one of these. They all use the same eggs and milk mixture.

1. Bacon and cheddar. Swap the sausage for 12 slices of cooked, crumbled bacon.
2. Ham and Swiss. Use 2 cups (300g) of diced ham and swap the cheddar for Swiss cheese. Great for using up leftover holiday ham.
3. Vegetarian. Skip the meat and add 3 cups of veggies instead, like sautéed mushrooms, spinach, peppers and onions. Squeeze the spinach dry first.
4. Tex Mex. Use chorizo or taco seasoned sausage, pepper jack cheese and a small can of diced green chiles. Serve with salsa and sour cream.
5. Bread instead of potatoes (strata). Swap the hash browns for 6 cups (about 300g) of day old bread cubes. Soak it overnight for the best texture.
6. Tater tot casserole. Top with a single layer of frozen tater tots instead of putting hash browns underneath. Kids love this one.
7. Cottage cheese protein version. Replace 1 cup of the milk with 1 cup (225g) of cottage cheese, blended or whisked in. It adds extra protein and makes it fluffier.

What to Serve with Breakfast Casserole

• Fresh fruit salad or a bowl of berries
• Buttery biscuits or toast
• Cinnamon rolls or banana bread for something sweet
• Coffee, orange juice or a fruit smoothie
• A simple green salad if you serve it for brunch

How to Store and Reheat

Fridge: Let it cool, then cover the dish or move squares into an airtight container. It keeps for up to 4 days.

Freezer: Wrap single squares in plastic wrap and then foil, and freeze for up to 3 months. Thaw overnight in the fridge.

Reheating: Microwave a single square for 60 to 90 seconds. To warm a larger amount, cover with foil and bake at 350°F (175°C) for 15 to 20 minutes.

My Tips for the Best Breakfast Casserole

• Squeeze the hash browns dry. Extra water is the number one reason breakfast casseroles turn out soggy.
• Drain the sausage well. Grease pools at the bottom of the dish if you skip this.
• Use freshly shredded cheese. Bagged cheese has a coating that stops it from melting as smoothly. It still works, but block cheese is better.
• Do not overbake. Take it out when the center is just set. It keeps cooking a little as it rests.
• Let it rest before cutting. Ten minutes makes the difference between clean squares and a messy scoop.

Breakfast Casserole FAQs

Can I make breakfast casserole the night before?

Yes. Assemble it, cover it and keep it in the fridge for up to 24 hours. Bake it in the morning, adding about 10 to 15 minutes to the baking time.

How do I know when breakfast casserole is done?

The top should be golden, the edges should pull away slightly from the dish, and a knife in the center should come out clean with no runny egg. The center should reach 160°F (71°C).

Why is my breakfast casserole watery?

Usually the hash browns were not squeezed dry, the vegetables were added raw, or the casserole was underbaked. Cook watery vegetables first and squeeze the potatoes well.

Do I need to thaw the hash browns?

Thawing is best because you can squeeze out the water. If they are frozen, add 10 to 15 minutes to the baking time and expect a slightly softer texture.

Can I cut this recipe in half?

Yes. Halve every ingredient and bake in an 8×8 inch (20×20 cm) dish for about 35 to 45 minutes.

Can I make it without milk?

Yes. Use unsweetened almond or oat milk. The texture will be a little less creamy but still very good.

Final Thoughts

If you only learn one make ahead breakfast, make it this one. It is cozy, filling and so easy, and it makes any morning feel a little bit special. Try the classic sausage version first, then have fun with the variations.