Butternut Squash and Spinach Breakfast Casserole

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This easy Butternut Squash and Spinach Breakfast Casserole is filling, packed with veggies, and delicious. Serve it for breakfast, lunch, or dinner!

251 CAL 12g CARBS 15g FAT 19g PROTEIN 4

This easy Butternut Squash and Spinach Egg Casserole is healthy, easy to make, and perfect for meal prep or a fancy brunch.  The combination of butternut squash, spinach, and feta ranks up there as one of my favorites, especially when it's all baked together in a tasty breakfast dish like this.

Lately, I have been enjoying making a big savory egg dish or breakfast casserole on Sundays that I can just use as a grab-and-go meal during the week as part of my meal planning. It makes breakfast easy and mindless, which is exactly what I need when the coffee kicks in. Plus, the protein from the eggs keeps me full all morning and I don't find myself reaching. for snacks.

The other thing I love about this is how versatile it is. Make it with different combinations of veggies, try out different cheeses, use sweet potatoes instead of butternut squash - the options are endless.

Why You'll Love This Butternut Squash Breakfast Casserole

  • Nutritious: Butternut squash is rich in vitamins, minerals, and fiber. Spinach is packed with iron, antioxidants, vitamins, and minerals. Eggs are a great source of protein making this breakfast healthy, filling, and a great way to start the day.
  • Versatile: Breakfast casseroles like this are so easy to customize! Switch out the veggies, add bacon or sausage, and try it with different cheeses.
  • Serve it for breakfast, lunch, or dinner:  Add breakfast potatoes and turkey bacon for breakfast or salad and soup for lunch or dinner. Think of it like a frittata or quiche.

Looking for more delicious butternut squash breakfast dishes? Try this Butternut Breakfast Casserole with Sausage, this Breakfast Salad, or Breakfast Burrito Bowls (just swap butternut squash for the sweet potatoes.)

Ingredients and Substitutions

Here is everything you need for this tasty breakfast.

  • Eggs: Eggs are the base of this hearty breakfast casserole. Use whole eggs, egg whites, or a combination of the two. Add a touch of milk or half and half (or cream) for a creamier consistency.
  • Butternut squash: Butternut squash is the star of this dish. Use fresh peeled butternut squash or speed up prep by using frozen butternut squash cubes. Cook them right from frozen in the skillet with the onion. Just make sure to drain out any excess water. You can swap in another type of squash or sweet potatoes as well.
  • Spinach: Spinach adds color, flavor, and nutrition to this recipe. Use any greens you like including kale, arugula, or cabbage. Just make sure it is fully cooked and tender.
  • Onion: Red onion adds some natural sweetness and tang to this recipe. Use any onions you like or swap in green onions or shallots for a milder flavor.
  • Spices: It's important to add kosher salt and pepper to eggs or they end up tasting blend. Additionally, add garlic powder (or fresh minced garlic) and oregano. Butternut squash is also delicious with sage, rosemary, or fresh herbs. 
  • Cheese: Feta cheese is a great way to layer in more flavor to this dish. It's also really good with goat cheese, shredded sharp cheddar, Swiss cheese, or Parmesan. Leave out the cheese for a dairy-free option.

How to Make Butternut Squash Breakfast Casserole

Here's how to make this easy breakfast casserole.

1. Saute the butternut squash, onions, and spinach

It's important to cook the vegetables before adding them to the casserole or they will release liquid into the casserole and change the texture. Start by heating olive oil in a large skillet. Add the onion and diced butternut squash. Cook for 8-10 minutes until the butternut squash is fork tender.  Season with salt, pepper, and spices. Stir in spinach until it wilts.

Taste and season if needed, but remember that feta cheese is salty, so do not over-salt the vegetables.

If you are using frozen butternut squash, start with just the onions and add the butternut squash after the onions cook for a couple of minutes. 

Roasting option: You can also roast the butternut squash and onions at 425 degrees for 20-25 minutes until fork tender.

2. Assemble the casserole and bake

Start by whisking the eggs and feta cheese until everything is well combined. Spray a baking dish with cooking spray and then add the butternut squash, spinach, and onions. Pour the eggs over top.

Bake for 20-25 minutes until the eggs are just set. Make sure not to overcook the eggs or the casserole will taste dry. The eggs continue to cook after they come out of the oven, so don't worry if they seem slightly soft.

Ideas for Customizing Butternut Squash and Spinach Breakfast Casserole

The great thing about this meal is that there are so many ways to make it your own!

  • Swap in different vegetables: Sub out the butternut squash for any other squash or veggies that you like. Asparagus, zucchini, yellow squash, or broccoli will work well here.
  • Use kale: You can use kale instead of spinach — or both!
  • Add more protein: Add cooked bacon, turkey sausage, chicken sausage, or beans to the casserole for more protein. 
  • Egg whites: You can use some egg whites or Egg Beaters instead of whole eggs if you like.
  • Add Mediterranean flavors: Add black olives, capers, artichoke hearts, or roasted red peppers to give the dish more of a Mediterranean taste.
  • Add crust: Add biscuit dough to the bottom of the pan first, if you want a little bit of bread with your casserole (you might have to adjust the cooking time).
  • Serve it as a breakfast sandwich: Better yet, add a slice of this casserole between two pieces of sprouted grain bread with sliced avocado for an even more nutritious breakfast.
  • Make a breakfast bowl: Turn this into a breakfast bowl with greens, avocado, hot sauce or salsa, and canned black beans, rice, or quinoa.
  • Turn it into butternut squash hash: If you don't feel like baking a casserole, turn this into a breakfast hash by topping the cooked butternut squash, onions, and spinach with scrambled or fried eggs. Finish with feta cheese and herbs, similar to this Hippie Hash or Sweet Potato Hash.

Side view of butternut squash and spinach egg casserole with blurred background.

What Makes this Breakfast Casserole Healthy?

It's always good to start the day off on a healthy note I think. And this dish is no exception. It's chock full of healthy ingredients that all do good things for your body.

  • Olive oil is a great base oil that's good for cooking with and for adding to salad dressings, marinades, and a whole lot of other foods. It provides the good kind of heart-healthy fat and antioxidants.
  • Butternut squash is full of fiber, vitamin A, and potassium. It's also low calorie and has protein, iron, and vitamin C as well.
  • Red onions contain flavonoids and phytochemicals which help to ward off disease, cancer, and infection.
  • Spices like salt, garlic powder, oregano, and pepper not only make your food flavors soar, but they also deliver nutrients like vitamins, minerals, and anti-inflammatory properties that keep your body healthy.
  • Spinach is chock full of iron; vitamins A, C, and K1; protein; and fiber and it's low-carb and low-calorie.
  • Eggs provide healthy cholesterol, protein, and antioxidants, and are very filling, despite being a low-calorie food.
  • Reduced-fat feta cheese is a salty cheese that has less fat than other cheeses. It also contains zinc, folate, selenium, vitamin B6, and zinc.

How To Prepare and Cook Butternut Squash

Butternut squash is tough to cut so you'll need a sharp knife and vegetable peeler. First, take off the top and bottom of the squash to make a flat surface. Then use a vegetable peeler to remove the skin. Cut the squash in half, remove the seeds, then go about dicing it up as you would any other vegetable. It will just take a little longer, but it's worth the effort.

For cooking it, you can saute it as I did here for this recipe, bake it whole like this whole roasted butternut squash,  and turn it into fries like these Butternut Squash Fries. Or, you can cook it and blend it up into butternut squash soup.

Butternut Squash and Spinach Egg Casserole in a pan with a cutting board underneath.

How to Use Egg Casserole in Meal Planning: Leftovers and Storage

This casserole is great for meal planning. I'll make it on Sunday and have enough servings to have it every breakfast again for the rest of the week. It's so much easier than you think and so worth the work in advance.

  • Let the casserole fully cool and then cut into individual servings. Store in an airtight container for 4-5 days in the fridge. 
  • East cold, room temperature, or warmed up. 

Frequently Asked Questions

Here are the most common questions about making this butternut squash and egg casserole.

Butternut squash and sweet potatoes are similar in taste, texture, and color. Butternut squash tends to have less sweetness and a bit more earthy flavor than sweet potatoes. Butternut squash also has a softer texture.

Slice of butternut squash, spinach, and egg casserole on a plate.
The Recipe
Butternut Squash and Spinach Breakfast Casserole in a cast iron skillet with a napkin.

Butternut Squash and Spinach Breakfast Casserole

251 CAL 12g CARBS 15g FAT 19g PROTEIN 4
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  • 1 tbsp olive oil
  • 3 cups butternut squash, peeled and diced
  • 1/2 red onion, diced
  • 3/4 tsp salt
  • 3/4 tsp garlic powder
  • 3/4 tsp oregano
  • 3/4 tsp pepper
  • 6 cups spinach, chopped
  • 12 eggs
  • 1 cup reduced fat feta cheese

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Preheat the oven to 400 degrees. Add the olive oil to the pan. Once hot, add the butternut squash and red onion. Cook for 8-10 minutes until squash and onion are tender, adding 1-2 tablespoons of water if burning. Add the salt, garlic powder, oregano, and pepper. Stir together. Add the spinach and cook until it wilts, 1-2 minutes.

Diced butternut squash cooking in a skillet.

Whisk together the eggs and feta. Add the butternut squash mixture to a baking dish sprayed with cooking spray. Pour the eggs over top. Bake for 20-25 minutes until eggs set and are cooked through.

Baked butternut squash, egg, and spinach casserole in a skillet.


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Nutritional Facts
Serving Size: 1 piece
Amount Per Serving
Calories 251
Calories from Fat 132
% Daily Value *
Total Fat 15g
Saturated Fat 5g
Monounsaturated Fat 0g
Polyunsaturated Fat 0g
Cholesterol 381mg
Sodium 767mg
Total Carbohydrate 12g
Dietary Fiber 2g
Sugars 2g
Protein 19g

* Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.

The Nutritional Values provided are estimates only and may vary based on the preparation method.


Use frozen butternut squash to speed things up and avoid having to peel and dice the squash.

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About the author Meet Kristen McCaffrey
Hi, I’m the cookbook author, recipe developer, and food enthusiast behind Slender Kitchen. I am obsessed with making healthy food that is easy to prepare and absolutely delicious. Meal planning is my secret weapon and I hope I can make meal time easier for you with our tried and tested recipes and foolproof meal plans. Learn More
On Butternut Squash and Spinach Breakfast Casserole
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October 25, 2023 - 17:34
Could you use frozen butternut squash in this recipe and if so would it have to be thawed?
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October 26, 2023 - 08:57
Frozen butternut squash would work great. You can either cook it in the pan from frozen or defrost it, both will work. If you cook it from frozen., just keep an eye on it so it doesn't burn on the outside.
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