Creating Baked Spaghetti Squash Casserole is simple when you follow these steps:

1. Preheat the Oven: Preheat your oven to 400°F (200°C).

2. Prepare the Spaghetti Squash: Cut the spaghetti squash in half lengthwise and scoop out the seeds. Rub the inside with olive oil, salt, and pepper.

3. Roast the Squash: Place the squash halves, cut side down, on a baking sheet lined with parchment paper. Roast in the preheated oven for about 30-40 minutes, or until tender.

4. Cook the Protein: While the squash is roasting, prepare your ground turkey or your preferred protein according to package directions. Set aside.

5. Make the Filling: In a mixing bowl, combine ricotta cheese, the egg, dried Italian herbs, and half of the mozzarella and Parmesan cheeses. Mix until smooth.

6. Combine Ingredients: Once the squash is cool enough to handle, use a fork to scrape the insides into strands. Mix these strands with the cooked protein and marinara sauce in a large bowl.

7. Assemble the Casserole: In a greased 9×13 inch baking dish, layer half of the squash mixture. Spread the ricotta mixture evenly on top, then add the remaining squash mixture on top.

8. Top with Cheese: Sprinkle the remaining mozzarella and Parmesan cheeses over the final layer.

9. Bake: Place the assembled casserole in the oven and bake for an additional 20-25 minutes, or until the cheese is bubbly and golden.

10. Cool and Serve: Remove the casserole from the oven and let it cool for about 15 minutes. Garnish with fresh basil or parsley if desired.

These steps are designed to guide you through the process of preparing this incredible casserole effortlessly.