Healthy Lunch Casserole

Ingredients

• 2 teaspoons olive oil
• 1 pound extra-lean ground turkey
• 1/2 onion, chopped
• 3/4 teaspoon salt, divided
• 1/2 teaspoon ground pepper, divided
• 2 portobello mushrooms, stems removed and gills scraped, cut into 1-inch pieces
• 1 1/4 cups zucchini, chopped to a 3/4-inch dice
• 3 large cloves garlic, minced
• 3/4 teaspoon dried oregano
• 1/4 teaspoon red pepper flakes
• 1 (28-ounce) can crushed tomatoes
• 1 3/4 cups brown rice, cooked
• 1/2 cup parmesan cheese, grated and packed, divided
• 3 teaspoons flat-leaf parsley, minced, plus more, to taste, for garnish