Tender, fork-string spaghetti squash tossed with shredded chicken, wilted spinach and a savory tomato sauce, then finished with bubbling Parmesan for a crisp, golden top—comforting and low-carb without skimping on texture.
This easy weeknight casserole comes together quickly and is ready in 55 minutes total, making it perfect for busy evenings or casual family dinners; slice and serve hot so the cheesy top is still browned and slightly crunchy.
Why You’ll Love This Recipe
A low-carb weeknight casserole that swaps pasta for roasted spaghetti squash while delivering hearty, familiar Italian flavors in about 55 minutes total time.
If you enjoy one-dish casseroles with vegetables and cheese, try the flavorful Cheesy Broccoli Rice Casserole for another family-friendly option.
Ingredients You’ll Need
How to Make the Casserole
- Preheat the oven to 375 °F so it reaches temperature while you prepare the squash and other components.
- Cut the spaghetti squash in half lengthwise and scoop out the seeds. Drizzle the cut sides with 2 teaspoons extra-virgin olive oil, sprinkle with 1/2 teaspoon sea salt and 1/2 teaspoon black pepper.
- Line a baking sheet with parchment paper, place the squash halves cut-side down on the sheet, add 1/4 cup water to the sheet, and bake at 375 °F for about 30 minutes until the flesh is fork-tender; remove from the oven and let cool slightly.
- When the squash is cool enough to handle, use a fork to scrape the flesh into long strands into a medium mixing bowl and set aside. Let the strands rest a few minutes so excess steam and liquid dissipate.
- In a small skillet over medium heat, warm 1 teaspoon extra-virgin olive oil and sauté 1 clove crushed garlic until fragrant, then add 3 handfuls fresh spinach and cook until wilted; transfer the spinach and garlic to the bowl with the squash.
- Add 1 lb. pre-cooked shredded chicken, 1 cup tomato sauce, 1 egg, 1 tablespoon garlic powder, 1 1/2 tablespoons Italian seasoning, 1/2 teaspoon red pepper flakes, 1/2 teaspoon freshly ground pepper, and 1/2 teaspoonsalt to the squash and spinach; mix until everything is evenly combined. Stir in 1/4 cup fresh Parmesan if using, and taste—adjust salt and pepper before baking.
- Transfer the combined mixture to a baking dish, smoothing the top. Sprinkle additional fresh Parmesan and a pinch of red pepper flakes over the surface if desired.
- Bake at 375 °F for 10 minutes to warm through and set the mixture.
- Move the casserole under the broiler on high for 3-5 minutes, watching closely until the cheese is bubbling and browned to your liking—stay attentive because broilers can brown fast.
- Remove from the oven and let the casserole rest for a few minutes so it firms slightly; then cut into portions and serve warm while the top is still crisp and golden.
Prevent Watery Squash
Spaghetti squash can hold a lot of steam and release water when mixed into a casserole; follow the roast-cut-scrape-drain sequence to keep the filling from becoming soupy.
- Roast cut-side down with 1/4 cup water as instructed—this steams the squash and shortens roast time while preserving texture.
- After scraping the strands into a bowl, let them rest for several minutes in a colander or on paper towels to release liquid.
- Optionally pat the strands lightly with paper towels or wrap them in a clean kitchen towel and press to remove extra moisture before mixing.
Bake-and-Broil Finish
Baking the assembled casserole warms and sets the filling, while a brief high broil creates the desirable browned, slightly crisp cheese crust that mimics a traditional baked pasta top.
- Bake at 375 °F first to heat through and let the egg binder set.
- Broil on high for 3-5 minutes to brown the cheese—place the oven rack about 6 inches from the broiler element and watch continuously.
- If the top browns too quickly, slide the dish down one rack or finish under ambient oven heat to avoid burning.
Make-Ahead & Freeze
This casserole is friendly to short-term make-ahead planning and freezing when assembled ahead. Parmesan tastes best when added fresh right before broiling, so reserve extra for the final step.
- Refrigerate assembled, unbaked casserole (covered) for up to 24 hours; bake from cold at 375 °F and expect to add about 5-10 minutes to the bake time.
- For longer storage, freeze the assembled casserole in a freezer-safe dish for up to 2 months. Thaw overnight in the refrigerator before baking.
- If baking from fully frozen, bake covered at 375 °F until heated through (roughly 45-55 minutes depending on dish size), then uncover and broil 3-5 minutes for a browned top.
Tips for Success
Avoid a watery casserole: After roasting and scraping, let the squash strands sit in a colander or on paper towels for a few minutes to drain; gently press to remove excess liquid before mixing.
Chicken options: Use baked or boiled shredded chicken as noted; rotisserie or leftover roasted chicken also works—taste and adjust seasoning since pre-cooked proteins can vary in salt.
Watch the broiler: Broil for exactly 3-5 minutes and stand by the oven—the top should bubble and brown, not blacken. If it’s browning too quickly, move the rack down or finish under the oven heat alone.
Make it cheesier: For a stronger crust, add more fresh Parmesan on top just before broiling or sprinkle a little shredded mozzarella for extra melt.
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Final Notes
This Italian-style spaghetti squash casserole is an easy way to enjoy classic baked-casserole flavors while keeping the dish lower in carbs—perfect for busy weeknights or make-ahead dinners.
Taste and adjust seasoning before the final bake, reserve extra Parmesan for broiling, and slice into warm portions so each serving keeps a crisp, cheesy top.
Italian-Style Spaghetti Squash Casserole
Ingredients
- 1 Spaghetti squash sliced in half and seeds scooped out
- 2 teaspoons extra-virgin olive oil
- 1/2 teaspoon sea salt
- 1/2 teaspoon black pepper
- 1 teaspoon extra-virgin olive oil
- 1 clove garlic crushed
- 3 handfuls fresh spinach
- 1 lb organic boneless chicken breasts baked or boiled and shredded
- 1 cup tomato sauce of choice homemade or store-bought
- 1 egg
- 1 1/2 tablespoons Italian seasoning more to taste
- 1/2 teaspoon red pepper flakes more to taste
- 1 tablespoon garlic powder
- 1/2 teaspoon freshly ground pepper
- 1/2 teaspoon salt
- 1/4 cup fresh parmesan cheese optional; more for topping
Instructions
- Preheat oven to 375 °F.
- Cut the spaghetti squash in half and scoop out the seeds, then drizzle the cut sides with olive oil, sea salt, and black pepper.
- Line a baking sheet with parchment paper.
- Place the squash halves cut-side down on the prepared baking sheet, add 1/4 cup water to the sheet, and bake about 30 minutes until the flesh is fork-tender; let cool.
- When cool enough to handle, scrape the squash flesh into a medium mixing bowl using a fork and set aside.
- In a small skillet over medium heat, warm the oil and sauté the crushed garlic until fragrant, then add the spinach and cook until wilted.
- Add the sautéed spinach and garlic, shredded chicken, tomato sauce, egg, garlic powder, Italian seasoning, red pepper flakes, freshly ground pepper, and salt to the bowl with the spaghetti squash; mix until well combined. Stir in the Parmesan if using.
- Transfer the combined mixture to a baking dish.
- Sprinkle the top with fresh Parmesan and additional red pepper flakes, if desired.
- Bake at 375 °F for 10 minutes, then broil on high for 3-5 minutes or until the cheese is bubbling and browned.
