Add the spinach just before serving to preserve its bright color and fresh flavor.
1 tablespoon olive oil
½ pound ground turkey
1 onion, chopped
1 carrot, sliced
1 stalk celery, chopped
6 cups chicken broth
½ cup pearl barley
Kosher salt and black pepper
3 cups baby spinach, chopped
Heat the oil in a large saucepan over medium-high heat. Add the turkey and cook, breaking it up with a spoon, until browned, 3 to 5 minutes; transfer to a plate.
Add the onion, carrot, and celery to the saucepan and cook, stirring often, until softened, 3 to 5 minutes.
Return the turkey to the pan and add the broth and barley; season with ¾ teaspoon salt and ¼ teaspoon pepper. Reduce heat and simmer until the barley is tender, 25 to 30 minutes. Stir in the spinach.