Preheat the oven to 375°F (190°C).

Prepare the spaghetti squash by cutting it in half lengthwise and removing the seeds.

Place the squash halves cut-side down on a baking sheet and roast for 30-40 minutes.

Once cooked, allow the squash to cool slightly, then scrape the flesh into a bowl with a fork.

In a mixing bowl, combine the scraped spaghetti squash, ricotta cheese, half the mozzarella cheese, ground turkey, bell peppers, eggs, oregano, salt, and pepper.

Spread the mixture into a greased 9x13-inch baking dish.

Sprinkle the remaining mozzarella and Parmesan cheese over the top.

Cover the dish with aluminum foil and bake for 25 minutes.

Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.

Let the casserole cool for a few minutes before serving.