Creamy Spaghetti Squash Turkey Casserole with Gruyère and Spinach

There’s something incredibly comforting about a bubbling hot casserole on a cool evening, especially when it’s creamy, savory, and packed with nourishing ingredients.

For me, this spaghetti squash turkey casserole feels like a warm hug in a dish.

The tender squash strands melt into the creamy Gruyère sauce, and the golden turkey-spinach mixture brings depth and heartiness.

Add a crunchy layer of French-fried onions on top—and honestly, I’m in heaven.

Why I Love This Spaghetti Squash Turkey Casserole

It’s the kind of cozy, feel-good dish I crave when the weather turns cool.

The roasted spaghetti squash adds a subtle sweetness and keeps things light.

The creamy Gruyere sauce brings incredible richness without feeling heavy.

It’s secretly loaded with veggies—perfect for a balanced, satisfying meal.

I love that it can be made ahead and baked when ready to serve.

And the golden, crispy French fried onion topping? Absolute magic.

What You’ll Need (Ingredient Highlights)

Spaghetti Squash – Roasted until soft, then shredded into noodle-like strands. The perfect pasta swap.

Ground Turkey – Lean, flavorful protein that browns beautifully with onion and garlic.

Baby Spinach – Adds color and nutrients, and wilts perfectly into the mix.

Gruyère Cheese – Nutty and melty, it creates that luxurious sauce we all love.

Creamy Gruyère Sauce – A homemade béchamel flavored with garlic, Italian seasoning, and a hint of nutmeg.

French Fried Onions – The crispy finish! Adds texture and a little indulgence to the dish.

Pro Tips Before You Start

Don’t skip roasting the squash cut-side down. It keeps the strands tender but not watery.

Use freshly grated Gruyère for best meltability and taste.

Taste your sauce before assembling—it should be flavorful on its own.

Add more thyme or sage if you love those cozy fall flavors.

How to Make Spaghetti Squash Turkey Casserole

Step 1: Roast the Squash

Preheat oven to 400°F and line a baking sheet with foil.

Drizzle olive oil over the cut sides of the spaghetti squash and season with salt, pepper, granulated onion, and granulated garlic.

Place squash halves cut-side down on the baking sheet and roast for about 1 hour until tender.

Step 2: Sauté the Onions and Turkey

In a large skillet, heat olive oil over medium-high heat.

Sauté the sliced onions with salt and pepper until caramelized, about 10 minutes.

Add the ground turkey, white pepper, more salt and pepper, and cook while breaking it up into crumbles.

Cook 2–3 minutes until golden.

Add garlic and stir, then toss in spinach. Let it wilt for about 1 minute.

Stir in sage and thyme. Set mixture aside.

Step 3: Prep the Squash

Once the squash is cool enough to handle, reduce oven to 375°F.

Use a fork to scrape squash strands into a large bowl.

Step 4: Make the Gruyère Sauce

In a saucepan, melt butter and sauté garlic briefly.

Sprinkle in flour and whisk to create a roux. Gradually whisk in milk.

Bring to a simmer, stirring constantly until thickened (about 5 minutes).

Season with salt, pepper, Italian seasoning, and a pinch of nutmeg.

Stir in grated Gruyère until fully melted.

Step 5: Assemble the Casserole

Combine squash strands with the creamy sauce and the turkey-spinach mixture.

Mix gently but thoroughly. Taste and adjust seasoning.

Lightly grease a 3-quart casserole dish and spoon in the mixture.

Sprinkle with additional Gruyère.

Step 6: Bake and Finish

Bake uncovered at 375°F for 20 minutes.

Top with French-fried onions and bake for 5 more minutes.

Garnish with fresh thyme leaves and serve hot!

What to Serve It With

This dish is super satisfying on its own, but if you want to round it out:

A simple green salad with lemon vinaigrette

Garlic bread or a crusty baguette

Roasted Brussels sprouts or green beans

Variations / Substitutions

Protein swap: Use ground chicken or Italian sausage instead of turkey.

Vegetarian version: Skip the meat and add sautéed mushrooms for umami.

Dairy-free option: Use plant-based butter, cheese, and milk for the sauce.

Herb twist: Swap sage for rosemary or tarragon for a different flavor note.

Storage & Leftovers

This casserole keeps well for 3–4 days in the fridge.

Reheat individual portions in the microwave or oven until hot.

You can also freeze it (without the fried onions) in airtight containers for up to 2 months.

Reheat from frozen in the oven at 350°F until bubbly.

FAQs

Can I prep this casserole in advance?
Yes! Assemble everything (except the fried onions), cover, and refrigerate overnight.

Add onions just before baking.

Do I need to squeeze the spaghetti squash dry?

Not usually. Roasting cut-side down helps prevent too much moisture.

But if it seems watery, blot with a paper towel.

Can I use other cheeses besides Gruyère?
Absolutely. Try sharp white cheddar, fontina, or a mix of mozzarella and Parmesan.

Is this casserole gluten-free?
Swap the flour for gluten-free all-purpose flour and ensure your fried onions are gluten-free.

How can I make it spicier?
Add crushed red pepper flakes to the turkey while sautéing or mix a bit of cayenne into the sauce.

What if I don’t have fresh sage or thyme?
Use dried herbs instead—about ⅓ the amount.

Dried herbs are more concentrated.

Can I make this low-fat?

Use low-fat milk and reduce the amount of cheese or choose a lighter one like part-skim mozzarella.

Final Thoughts

This spaghetti squash turkey casserole has everything I want in a comfort meal—warmth, creaminess, and a little crunch.

It’s cozy enough for fall but light enough for everyday dinners.

If you’re craving comfort food with a nutritious twist, this one’s a must-make.

Bonus: it tastes even better the next day!