Butternut Squash & Sausage Casserole

The first time I made this casserole, I was trying to use up a butternut squash that had been sitting on my counter for weeks. My husband came home from work, sniffed the air, and immediately asked what smelled like a fancy restaurant had moved into our kitchen.

Last autumn, my sister visited during a particularly rainy week and requested something cozy. I threw together this casserole on impulse. We ended up eating it straight from the baking dish while watching old movies, and she still texts me about it months later.

Ingredients

• 1 medium butternut squash: Peeling and cubing this yourself gives you control over the size, which helps everything cook evenly
• 1 pound Italian sausage: Sweet or spicy both work beautifully, but removing the casing lets the meat crumble and distribute throughout the dish
• 1 cup cooked quinoa: This adds nutty texture and protein, plus it holds up better than rice during the long bake
• 3 cups baby spinach: The spinach wilts down into the mixture almost invisibly, sneaking in nutrients without changing the flavor profile
• 1 cup shredded mozzarella and ½ cup grated Parmesan: The mozzarella creates those irresistible cheese pulls while Parmesan adds a salty, nutty finish
• 1 teaspoon dried thyme, sage, and paprika each: This herb trio bridges the gap between the sweet squash and savory sausage beautifully

Instructions

Preheat and prepare your baking dish:

Set your oven to 375°F and lightly grease a 9x13-inch baking dish with olive oil or cooking spray

Sauté the onion:

Heat 2 tablespoons olive oil in a large skillet over medium heat and cook the diced onion for about 5 minutes until translucent

Add the garlic:

Stir in the minced garlic and cook for just 1 minute until fragrant, being careful not to burn it

Brown the sausage:

Increase the heat slightly, add the Italian sausage, and cook for 7 to 10 minutes while breaking it apart with a wooden spoon until fully browned

Season and soften the squash:

Add the cubed butternut squash along with the thyme, sage, paprika, salt, and pepper, then cook for 5 to 7 minutes until the squash begins to soften

Combine everything:

Stir in the baby spinach and cooked quinoa, cooking just until the spinach wilts, then pour in the broth and simmer for 3 to 4 minutes

Transfer to the baking dish:

Spread the mixture evenly into your prepared baking dish and top with both the mozzarella and Parmesan cheeses

Bake covered:

Cover with aluminum foil and bake for 25 minutes to let everything meld together

Finish uncovered:

Remove the foil and bake for another 15 to 20 minutes until the cheese is bubbly and golden brown on top

Rest and serve:

Let the casserole cool for 5 minutes before garnishing with fresh parsley and serving

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This recipe became my go-to for new parents because it reheats beautifully and freezes well. I dropped a pan off at my neighbors house last winter when they brought their baby home, and the husband sent me a photo of an empty dish at midnight with just the caption help, we ate the whole thing.

Make It Your Own

Sometimes I swap the quinoa for cooked rice or farro when I want to change the texture. The beauty of this casserole is how forgiving it is with substitutions.

The Vegetarian Version

When my vegetarian friend comes over, I use plant-based sausage or sometimes cannellini beans instead. The beans actually add a creamy texture that works surprisingly well with the squash.

Planning Ahead

You can assemble the entire casserole up to 2 days before baking. Just cover it tightly and refrigerate, then add about 10 extra minutes to the baking time since everything will be cold going into the oven.

• If you prep this ahead, hold off on adding the cheese until right before baking
• The flavors actually develop and deepen overnight in the fridge
• This is one of those dishes that tastes even better as leftovers the next day

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There is something deeply satisfying about a bubbling, golden casserole coming out of the oven on a cold night. This is the kind of food that makes people feel at home.

Recipe FAQs

→ Can I make this butternut squash casserole ahead of time?

Yes, you can assemble the entire dish up to 2 days in advance and refrigerate it. When ready to bake, add a few extra minutes to the cooking time since you'll be starting from chilled.

→ What can I substitute for the Italian sausage?

For a vegetarian version, use plant-based sausage or cannellini beans. You could also use ground turkey or chicken sausage for a lighter option, adjusting the seasoning to maintain the savory flavor profile.

→ Is this dish naturally gluten-free?

The base ingredients are gluten-free, but you need to ensure your sausage and broth are certified gluten-free. Some sausage brands contain wheat-based fillers, and some broths use barley-based seasonings.

→ Can I use other grains instead of quinoa?

Absolutely! Cooked rice, couscous, or even farro work well as substitutes. Just keep the quantity similar to maintain the proper texture and moisture balance in the casserole.

→ How do I store leftovers?

Store cooled leftovers in an airtight container in the refrigerator for up to 4 days. Reheat in the microwave or oven at 350°F until warmed through. The casserole also freezes well for up to 3 months.