Heat olive oil over medium heat. Add onions and sauté for 3-4 minutes. Add carrots, celery, and garlic and sauté for another 2-3 minutes. Add stock, tomatoes, turkey tail, rosemary, oregano, thyme, salt and pepper, and orzo pasta. Bring soup to a simmer making sure to stir every few minutes so the pasta does not stick at bottom of the pot. Reduce heat to low and cook for about 10 minutes, making any adjustments to taste.
Add in chopped spinach and cook for 1 minute. Turn off heat and serve immediately.
Enjoy your delicious Italian orzo soup with turkey tail mushroom!