Preheat oven to 350F (180C). Spray a 9 x 13-inch baking dish with cooking spray and set aside.
In a large skillet, heat about 2 teaspoons of olive oil over medium-high heat. Cook turkey, onion, and garlic in the skillet until no longer pink. Drain off any fat and return meat to the skillet. Season with salt and pepper, to taste.
Stir in zucchini and cook over medium heat for about 5 more minutes. Stir in rice, tomatoes, Italian seasoning, and Parmesan cheese. Pour mixture into prepared baking dish.
Top with mozzarella cheese. Bake, uncovered, for about 20-25 minutes (or until cheese is melted and casserole is bubbly).
Notes
Cooking for Just Two?Just cut the ingredients in half and prepare the casserole in an 8-inch square baking dish.Want to Prep Ahead? Prepare the casserole as instructed through Step 3. Top with the mozzarella cheese, allow to cool to room temperature, and then wrap tightly. Freeze the casserole for up to 3 months. When ready to bake, just thaw the casserole in the refrigerator overnight. Proceed with baking as instructed in Step 4.