Breakfast Casserole with Sausage

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This easy Make-Ahead Breakfast Casserole with Sausage and Fresh Potatoes can be assembled in the evening and baked in the morning. Or, you can even cook it in your slow cooker overnight. It feeds a crowd and is perfect for Thanksgiving or Christmas morning, or any time of year for breakfast, lunch, or dinner!

Overhead photo of breakfast casserole in a white baking dish.

Similar to a crustless quiche or frittata, this breakfast casserole has all your favorite ingredients mixed into one easy recipe and baked to savory perfection. It’s perfect for a crowd, especially since it’s gluten-free and grain-free and pretty low-carb, even with potatoes.

Sausage is the base, and the sausage flavor permeates throughout the casserole because the cooking grease is repurposed to sauté the veggies and potatoes. (Though you can certainly make this vegetarian by using a vegetarian sausage substitute or mushrooms).

The bell peppers and onions add great flavor without being overpowering, which I was worried about because I find bell peppers often overpower.

And the potatoes! Most breakfast casserole recipes use frozen hash browns in the mix. I wanted to use fresh potatoes in order to make it healthier (no preservatives) and more budget-friendly. It does take a little extra time to cook them up, but not too much time if you dice them up into small pieces. And sautéing the potatoes in the sausage grease until they’re browned adds a ton of flavor and great texture to the casserole!

Best of all, you can assemble this breakfast casserole and refrigerate overnight, and bake in the morning. You can even cook it in your slow cooker overnight!

Ingredients and Substitutions

  • Eggs
  • Shredded Cheddar Cheese – Or a similar melting cheese, such as Monterey Jack, mozzarella, etc.
  • Ground Sausage – Italian mild or hot pork sausage works well, or your favorite ground breakfast sausage. If it’s in casings, just remove the casings and discard before cooking.
  • Potatoes – I used red, but any will do. You can also use sweet potatoes, or cauliflower for a lower carb version.
  • Bell pepper – I prefer red for the flavor and color but any color will do.
  • Onion – yellow or white is best, but you can also use green onions (which can also be used for garnish).
  • Milk – preferably whole milk, but you can use low-fat if you like, or even half and half or heavy cream for a richer texture.
Close up photo of a slice of breakfast casserole with a fork taking a piece out of it.

How to make Breakfast Casserole

  1. COOK the sausage in a large skillet until it’s fully cooked. When it’s done, use a slotted spoon to remove it to a large bowl to leave the grease behind. If you don’t have a slotted spoon, you can tilt the pan to let the grease go to one side and then scoop the sausage out.
  2. RESERVE the sausage grease, leaving about 2 tablespoons in the skillet.
  3. COOK the potatoes in the sausage grease with a pinch of salt and pepper until browned tender. You can cover the skillet and add a splash of water to speed up the cooking process if you like. Add to the bowl.
  4. COOK the peppers and onions in some more sausage grease until browned and tender. Add to the bowl.Process collage showing cooking sausage, potatoes, peppers, and onions in a skillet.
  5. MIX eggs, cheese, milk, salt, and pepper in another large bowl.
  6. COMBINE everything together in one bowl.
  7. GREASE a large baking dish (I used 9×13, but something equivalent or slightly smaller will do) with some of the reserved sausage grease.
  8. POUR in the batter. At this point, you can cover with foil and refrigerate until you are ready to bake.Process collage showing mixing the ingredients for breakfast casserole and pouring it into a baking dish.
  9. When you are ready to bake, BAKE at 350 degrees F for 45-55 minutes, until it no longer jiggles.
  10. COOL for about 10 minutes until you slice and serve. Garnish with green onions if you like.

How to make breakfast casserole in your slow cooker

Just follow the directions as written, but instead of adding the mix to a greased baking sheet, add it to your greased crockpot.

Cook it on low for 7-8 hours, which is great for overnight. Or cook on high for 2.5-3 hours- perfect for a late breakfast or brunch!

FAQs

1. How far in advance can I make it?

You can make this anywhere from 2 hours to 48 hours in advance. Just cover, refrigerate, and bake when ready!

2. How long do leftovers stay good for?

The leftovers stay good for 3-5 days are are DELICIOUS reheated. In fact, you can bake this whole thing in advance if you like and just reheat slices in the microwave, or stick the whole thing in the oven covered with foil for about 15-20 minutes to warm up at 325 degrees if you prefer.

3. Can I freeze it?

Yes! You can freeze the cooked breakfast casserole for up to 3 months, wrapped tightly in plastic wrap, foil, or a zip top bag with as much air squeezed out as possible. The texture may be a little different after freezing, but still yummy.

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Other make ahead breakfast recipes to feed a crowd

Looking for more ways to feed a large group of people for breakfast or brunch, or just want leftovers to last for the week? Here are some of my favorite breakfast recipes that can be made ahead and yield a generous amount.

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Breakfast Casserole

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Assemble this make ahead breakfast casserole recipe with sausage, peppers, and fresh potatoes and bake in the morning or slow cook overnight!

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Servings: 12 servings

Calories: 267kcal

Author: Elizabeth Lindemann

Ingredients

  • 1 lb. ground sausage Italian mild or hot pork sausage works great, casings removed if needed.
  • 1 cup diced potatoes I used about 2 small red potatoes diced into small, 1/4″ pieces
  • 1 bell pepper diced (any color)
  • 1 onion diced
  • 10 large eggs
  • 2 cups shredded cheddar cheese or similar
  • 1 cup milk preferably whole
  • kosher salt and black pepper
  • sliced green onions for serving, optional

Instructions

  • If baking right away, preheat your oven to 350 degrees and place a rack in the center of the oven.

  • Cook the sausage (1 lb.) in a large skillet over medium-high heat, crumbling finely as you go (about 3-5 minutes). Use a spoon to transfer the cooked, crumbled sausage to a large bowl, leaving behind about 1-2 tablespoons of the grease (reserve any extra beyond that).

  • Add the diced potatoes (1 cup) to the skillet along with a generous pinch of salt and pepper. Sauté over medium-high heat, stirring occasionally, until potatoes are browned and tender, about 7-10 minutes. (You can stick a fork in them to tell if the are tender. To speed up the cooking process, you can add a little splash of water to the skillet and put a lid on it, which will trap the steam and result in faster cooking, adding water as needed between stirring.) Transfer the cooked potatoes to the bowl with the sausage.

  • Add 1 tablespoon of the reserved grease to the skillet (or just some butter or oil if you don’t have any) if the skillet seems dry. Then, add the diced peppers and onions and cook until browned and soft (about 3-5 minutes). Add them to the bowl with the sausage and potatoes.

  • In another medium-large mixing bowl, whisk together the eggs (10), the shredded cheddar cheese (2 cups), milk (1 cup), and 1/2 teaspoon each kosher salt and black pepper (see notes). Pour into the bowl with the sausage and veggies and stir to combine everything.

  • Use about 1 tablespoon of the cooking grease or butter/oil to grease a 9×13 (or similar) baking dish. Pour the mixture into the dish and spread out to make sure everything is distributed evenly.

  • At this point, you can bake right away or cover with foil and refrigerate (for up to 48 hours). When you are ready to bake, cook it at 350 degrees on the center rack for about 45 – 55 minutes, or until the casserole is set and doesn’t jiggle when you shake it (it will take on the longer side of things if it’s cold out of the fridge). Allow the casserole to cool for 5-10 minutes before slicing it into 12 pieces and serving. Garnish with sliced green onions, if desired.

Notes

  • On added salt: If the sausage has a really high amount of salt and seasoning, you may omit the added salt and pepper in the egg mixture. Do this for a lower sodium option as well and season individual portions as needed after baking.
  • Make it vegetarian: Use a vegetarian crumbled sausage substitute or sautéed mushrooms instead. You’ll need to use butter or oil for cooking and greasing the pan since you won’t have sausage grease.
  • Leftovers will stay good for 3-5 days in the fridge and are delicious reheated in the microwave for 30 seconds – 1 minute.
  • Slow cooker instructions: Mix everything and cook the veggies as directed, and spread out into a greased slow cooker and top with the extra cheese. Cook on low for 7-8 hours or high for 2.5-3 hours. Do this overnight for breakfast ready to go in the morning!
  • To save time, you can grate the potatoes instead of dice them.
  • If it’s browning too much on top, cover the casserole loosely with aluminum foil while it’s baking.
  • This recipe is already low in carbs, but to make it even lower carb/keto, use cauliflower instead of potatoes.

Recommended Equipment

Nutrition

Calories: 267kcal | Carbohydrates: 4g | Protein: 16g | Fat: 20g | Saturated Fat: 9g | Cholesterol: 185mg | Sodium: 420mg | Potassium: 252mg | Fiber: 1g | Sugar: 2g | Vitamin A: 758IU | Vitamin C: 14mg | Calcium: 185mg | Iron: 1mg