French Onion Spaghetti Squash
Cozy up with this autumn spin on a comfort food classic. It has all the indulgent flavors of French onion soup—sweet caramelized onions, creamy Gruyère, and a sprinkle of Parmesan—baked right into tender spaghetti squash.
Whether you’re hosting a cozy dinner party, whipping up an impressive weeknight meal, or meal-prepping for the week ahead, this French Onion Spaghetti Squash delivers rich, savory flavor with a healthier twist.
It’s bubbling and cheesy… with a lighter, veggie-packed twist! The squash naturally transforms into golden, spaghetti-like strands that soak up every drop of savory, oniony goodness. Each serving feels hearty and indulgent…and everything cooks right inside the squash “boat,” so you get a one-dish wonder with minimal cleanup!
Here’s a Joyful pro tip: Before slicing the squash (which tends to be a bit scary! Am I right?), pop it in the microwave for 4–5 minutes to soften it up. Not only does this make it much easier to cut in half, but it also ensures the squash cooks more evenly in the oven and shaves time off the roasting process. It’s a simple trick that I use all the time…it makes a big difference!
If you’re feeling creative, take it up a notch with a handful of sautéed spinach or kale for added greens, crispy bacon for indulgence, or even cooked chicken or tofu for a protein boost. And for a different presentation spin, you can transform this dish into a bubbling casserole by layering the ingredients in a baking dish (see notes below for more information on these variations).
This recipe is a way to enjoy the comforting flavors of French onion soup in a healthier yet decadent format—perfect for any occasion. I’m excited to share it with you!
Looking for more spaghetti squash recipes? Try my Spaghetti Squash with Creamy Hummus and Spinach Artichoke Dip Spaghetti Squash!
French Onion Spaghetti Squash
Ingredients
- 1 medium spaghetti squash
- 2 tablespoons olive oil, divided
- 1 teaspoon kosher salt, divided
- Black pepper, to taste
- 1 medium onion, thinly sliced
- ½ cup (heaping) grated Gruyère cheese
- 2 tablespoons grated Parmesan cheese
Instructions
- Preheat the Oven to 400°F (200°C). Microwave the spaghetti squash for 4–5 minutes to soften it slightly, making it easier to cut. Let it slightly cool, and carefully cut the squash evenly in half lengthwise. Scoop out the seeds and any stringy bits, then discard.
- Drizzle the inside of each squash half with 1–2 teaspoons of olive oil (or lightly mist with oil spray). Sprinkle with salt and black pepper. Place the halves “cut-side down” on a baking sheet and roast for 25–30 minutes, or until the flesh is tender and easily scraped into spaghetti-like strands with a fork. *Tip: Roast time may vary depending on the size of your squash. Start checking at the 25-minute mark by gently scraping one half with a fork. If the strands aren’t soft and tender yet, return it to the oven for 5 more minutes or so until perfectly cooked.
- While the squash roasts, caramelize the onions. Heat the remaining 1 Tbsp olive oil in a large skillet over medium heat. Add the thinly sliced onion and a pinch of salt. Cook, stirring every few minutes, for 8–10 minutes or until the onions are deeply browned and caramelized. Be careful not to burn them; lower the heat if necessary.
- Remove the squash from the oven and carefully flip the halves over—they’ll be very, very hot, so use a kitchen towel or flexible oven mitt for safety. Use a fork to scrape and fluff the interior, creating spaghetti-like strands.
- Assemble and Bake: Divide the caramelized onions and grated Gruyère evenly between the two squash halves, mixing them gently with the squash strands in each spaghetti squash shell. Sprinkle each half with 1 tablespoon of Parmesan cheese. Return the squash to the oven and bake for an additional 10 minutes, until the cheese is melted and bubbly. Garnish with optional minced parsley or thyme and enjoy!
Notes
- Cheese swaps: you can use Swiss cheese instead of Gruyère or add mozzarella for extra gooeyness.
- Boost the protein by add cooked pieces of chicken or tofu.
Add a handful of sautéed spinach or kale with the onions for added greens and extra nutrition. - Increase the indulgence by mixing in 1 to 2 tablespoons of crispy, cooked bacon.
You can transform this dish into a casserole by scooping the spaghetti squash strands into a baking dish, layering with the onion-cheese mixture, and baking until it’s warmed through, and the cheese is melty. - Sprinkle with a touch of smoked paprika or garlic powder for an extra flavor punch.
Hi, what would be the approximate weight for the squash? TIA.
Hi Roberta, Joy typically buys medium-size spaghetti squash, which is about 4 to 5 pounds. After microwaving for a few minutes and cutting in half, the cook time is ~25-30 minutes. But you can adjust for whatever squash you find at the store; a smaller one will require less time in the oven and a larger one will require more. We hope you love this recipe!
—Donna
My teenagers loved this! Heck, I loved this!
Hi Brenda, so glad you and your kids enjoyed the recipe! We know how picky teens can be so their approval definitely means a lot! Thanks for taking the time to share your thoughts with us—we truly appreciate the feedback!
—Donna
I love all your recipes. I do wish that you would include potassium level in the nutrition facts. I am on a low potassium diet. Thank you.
julie
Hi Julie and thanks for stopping by to share your thoughts! Unfortunately, we’re only able to show so many fields for our nutrition information—we can’t list every micronutrient. However, if you’re interested in specific recipes, please let us know by commenting on that particular recipe, and we’ll do our best to get back to you with the information as quickly as possible! If you were interested in this recipe, there’s 475 mg potassium per serving of French Onion Spaghetti Squash.
—Donna
Oh my gosh!! This was so delicious!! I split one tbls of parmesan between the two halves to cut down some of the caloires. After mixing the ingredients, I had some soon to turn fresh spinach, so I added that.
So very tasty and satisfying!! Love your recipes Joy!!
Hi Ruth, we’re so glad you love Joy’s recipes! Adding in some spinach sounds like a delicious and healthy idea!
-Alison
Absolutely delicious!! Will definitely make again.
Hi Trista, so glad the recipe was a hit and thanks for taking the time to share your thoughts with us!
—Donna
This sounds amazing! Do you have recommendations for making this recipe without a microwave? Thanks!
Hi K Ann, You don’t need a microwave for this recipe…it was simply to soften the spaghetti squash to make it easier to cut. Just be careful cutting the squash! Let us know if you choose to give it a go! — Eliza (Team Joy)
I have made this recipe several times now, and it’s a keeper! (We also love the pizza version!) It’s relatively simple and SO tasty! It’s a great recipe even if you’re not a spaghetti squash lover.
Note: If you don’t have a microwave, you can carefully cut the squash in half before cooking, but this time I baked it for a few minutes to soften it a bit before cutting and proceding with the recipe.
I regularly make Joy’s Go-To Tofu. Today I made the French Onion Spaghetti Squash to go with the tofu. It’s really good as well as really easy to make! I had baby broccoli on hand and put that with it as well. What a great veggie filled meal! I will definitely be making it again.
Hi Lisa, That sounds like such a perfect pairing! Love how you added baby broccoli too…what a colorful, nutrient-packed plate. So glad both recipes are becoming staples for you, and thanks for sharing! — Eliza (Team Joy)