Preheat your oven to 375°F (190°C) and prepare a medium-sized baking dish by spraying it lightly with cooking spray.

In a large skillet over medium heat, add a drizzle of olive oil. Add the ground turkey, cooking for about 5-7 minutes until browned.

In the same skillet, add another splash of olive oil and heat. Add the chopped onion and sauté for 3-4 minutes. Follow with minced garlic and red bell pepper; sauté for an additional 2 minutes.

Incorporate the sliced zucchini into the skillet, cooking for about 4-5 minutes. Stir in the drained diced tomatoes and sprinkle Italian seasoning.

Fold the browned ground turkey back into the vegetable mixture, combining everything thoroughly.

Spread the turkey and vegetable mixture evenly into your prepared baking dish. Top with shredded mozzarella and grated Parmesan cheese.

Place the baking dish in the preheated oven and bake for 20-25 minutes until cheese is bubbly and golden.

Remove the casserole from the oven and let it cool for about 5 minutes before serving.