Direction

1. Bring a large pot of lightly salted water to a boil. Stir in orzo and return to a boil. Cook pasta uncovered until partially cooked through but not yet soft, about 5 minutes; drain and rinse with cold water until cooled completely.
2. Meanwhile, heat olive oil in a large pot over medium heat. Add carrots, celery, and onion; cook and stir until vegetables begin to soften and onion becomes translucent, about 5 minutes. Add garlic; cook and stir until fragrant, about 1 minute more. Season mixture with thyme, oregano, bay leaf, salt, and black pepper; continue cooking another 30 seconds before pouring chicken broth into the pot.
3. Bring broth to a boil. Partially cover the pot, reduce heat to medium-low, and simmer until vegetables are just tender, about 10 minutes.
4. Stir orzo, lemon juice, and lemon zest into broth; add chicken. Cook until chicken and orzo are heated through, about 5 minutes. Add baby spinach; cook until spinach wilts into broth and orzo is tender, 2 to 3 minutes. Ladle soup into bowls; garnish with lemon slices and Parmesan cheese.