Easy potatoes O’Brien breakfast casserole is loaded with sausage, fluffy eggs, cheese, spinach and diced potatoes with onions and peppers. A hearty, make-ahead breakfast!

Easy Potatoes o'Brien breakfast casserole with sausage in a baking dish.

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Easy Breakfast Casserole

This easy Potatoes O’Brien breakfast casserole is one of those reliable dishes I turn to when I need something hearty and stress-free. If you love a cozy sausage hashbrown breakfast casserole or a classic egg potato casserole, this version with diced potatoes, peppers and onions is a flavorful twist that’s just as satisfying.

I recently served this at a brunch and everyone was asking for the recipe, so I figured I better get it up before the holidays! It’s ideal for hosting since you can assemble it ahead of time and bake it when you’re ready, just like my favorite make ahead breakfast casserole, and it slices beautifully for serving a crowd.

Ingredients Notes

Easy breakfast casserole ingredients including potatoes o'brien, cheese, eggs, spinach, garlic, milk, sausage and salt and pepper.

Find the full printable recipe with specific measurements below.

  • Breakfast sausage: Cook it ahead of time or just before assembling.
  • Eggs: The egg mixture is made with milk which helps to bulk up the eggs, making them nice and fluffy.
  • Frozen diced potatoes: I use O’Brien frozen diced potatoes. It comes as a mix with onions and bell peppers. Toss them in straight from frozen.
  • Chopped spinach: Roughly chop fresh baby spinach. You can use frozen spinach if preferred, just be sure to thaw it completely and wring out any excess water.
  • Shredded cheese: Pepper Jack cheese has a nice kick that I love, but you can use what you prefer.

How to Make an Easy Breakfast Casserole

Brown sausage in a large skillet over medium heat until no longer pink. Then, add the garlic and cook for another minute. Drain the grease.

Cooking breakfast sausage in a skillet for Easy Potatoes O’Brien breakfast casserole.

In a large bowl, beat the eggs with milk and stir in the frozen potatoes, chopped spinach, cheese, and cooked sausage. Season with salt and pepper.

Mixing eggs, diced O’Brien potatoes with onions and peppers, spinach, sausage and cheese for Easy Potatoes O’Brien breakfast casserole.

Pour the mixture into a greased 9×13 baking dish and sprinkle with the remaining cheese. Bake for 45 minutes until it’s firm and slightly golden brown. Let it rest for at least 10 minutes before slicing into 15-18 pieces.

Easy Potatoes O’Brien breakfast casserole in a baking dish with sausage, spinach, eggs and shredded cheese before baking.

Recipe Tips

  • Diced potatoes: You can use original diced potatoes (without pepper and onion) but may want to add additional seasonings for taste.
  • If browning too quickly, cover with foil for the remaining baking time.
  • Let cool slightly before slicing. It’s much easier to get clean slices this way.
  • Make it in advance: Assemble the casserole into the dish, cover it with plastic wrap, and refrigerate overnight until you’re ready to bake it the next day.
  • Serving suggestions: Serve a slice with a dollop of sour cream or complete your meal with refreshing rainbow honey lime fruit salad.
Sliced breakfast casserole with potatoes o'brien, sausage, spinach and cheese.

A few other breakfast and brunch casserole recipes include crescent roll breakfast casserole, cinnamon roll casserole and ham and cheese quiche.

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Easy Potatoes o'Brien breakfast casserole with sausage in a baking dish.

Potatoes O’Brien Breakfast Casserole

5 from 2 votes
Recipe by: Jamielyn Nye
Prep Time: 10 minutes
Cook Time: 45 minutes
Total Time: 55 minutes
Servings: 16
Easy potatoes O’Brien breakfast casserole is loaded with sausage, fluffy eggs, cheese, spinach and diced potatoes with onions and peppers. A hearty, make-ahead breakfast!
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Ingredients 

  • ½ pound breakfast sausage
  • 3 teaspoons minced garlic
  • 12 large eggs
  • 1 cup milk
  • 2 cups frozen diced potatoes O'Brien (mixed with onions and peppers -you don't have to thaw or cook the potatoes)
  • 1 cup chopped spinach , roughly chopped
  • 1 ½ cups shredded pepper jack cheese , divided
  • 1 ½ teaspoons salt
  • ½ teaspoon black pepper

Instructions

  • Prepare: Preheat the oven to 350°F. Grease a 9×13 baking dish with nonstick cooking spray.
  • Cook sausage: In a large skillet, brown 1/2 pound sausage over medium heat until fully cooked and no longer pink. Add 3 teaspoons garlic and cook one more minute. Place sausage on a plate that has been lined with paper towels to drain the grease.
  • Beat eggs and milk: In a large bowl, beat 12 eggs and 1 cup milk. Stir in the 2 cups frozen potatoes, 1 cup chopped spinach, 1/2 cup of the shredded cheese, and the cooked sausage. Add 1 1/2 teaspoons salt and 1/2 teaspoon pepper.
  • Bake: Pour the mixture into a baking dish and top with remaining 1 cup cheese. Bake for 45 minutes or until the eggs are firm and the top is slightly golden brown. Cover with foil if browning before the center is set.
  • Serve: Let rest for 10 minutes before cutting. Cut into 15-18 squares and serve warm.

Last step: Please leave a comment and rating after you make the recipe.

Notes

Make ahead: This casserole can be made in advance. Pour the mixture into the pan and refrigerate for up to 24 hours until ready to bake. You can also bake and then allow to cool to room temp, refrigerate and reheat the casserole at 250°F.
Customize: Swap sausage for leftover ham or bacon, kale for spinach or leave out. It’s also easy to sneak in extra veggies like mushrooms. 
Storage: Store leftovers in a covered container in the refrigerator up to 4 days. Reheat in the microwave or air fryer. 
Freeze: Wrap the slices in plastic wrap or foil and transfer them to a freezer bag for up to months. Thaw in the fridge overnight.

Nutrition

Calories: 162kcal, Carbohydrates: 6g, Protein: 10g, Fat: 11g, Saturated Fat: 5g, Polyunsaturated Fat: 1g, Monounsaturated Fat: 4g, Trans Fat: 0.04g, Cholesterol: 144mg, Sodium: 432mg, Potassium: 201mg, Fiber: 0.4g, Sugar: 1g, Vitamin A: 471IU, Vitamin C: 3mg, Calcium: 123mg, Iron: 1mg

Nutrition provided is an estimate. It will vary based on specific ingredients used.