Sauté the Vegetables: Heat the olive oil in a large soup pot over medium heat. Once hot, add the diced onion, celery, and carrots. Sauté for 5–6 minutes, stirring as needed, until the onion has softened.
Warm the Garlic: Add the minced garlic to the softened vegetables and stir for about 30 seconds, just until the garlic is warmed.
Build the Soup: Pour in the turkey broth, then add the drained diced tomatoes, pearl barley, bay leaves, rubbed sage, dried thyme, dried rosemary, salt, and pepper. Stir to combine the ingredients.
Simmer the Barley: Bring the soup to a simmer, then continue simmering for 45–60 minutes, until the pearl barley is fully cooked. The barley should be soft but still chewy, with no white center visible when a kernel is examined. Add the Turkey: Stir in the leftover turkey and continue simmering for another 5–10 minutes, until the turkey is heated through.
Adjust the Seasoning: Taste the soup just before serving and add more salt if needed, depending on the saltiness of the broth and your preference.
Garnish and Serve: Remove the bay leaves and garnish the soup with the optional fresh parsley before serving.
