Italian Turkey and Orzo Soup

Heat a large Dutch oven over medium- high. Add oil; swirl to coat. Add turkey; cook 6 minutes or until lightly browned, stirring to crumble. Add oregano, mushrooms, and garlic; sauté 5 minutes. Add stock, 2 cups water, salt, red pepper, and tomatoes, scraping pan to loosen browned bits; bring to a boil. Add orzo; cook 7 minutes. Stir in spinach and lemon zest; cook until the spinach wilts, about 2 minutes. Garnish with oregano, if desired.