In a large pot or deep skillet, heat the olive oil over medium heat.
Add the onion, garlic, carrots, and celery. Sauté for about 5 minutes, or until softened.
Stir in the salt, pepper, and thyme.
Add the orzo, chicken broth, and shredded chicken. Stir well and bring to a gentle boil.
Reduce the heat and let it simmer uncovered for 10–12 minutes, stirring occasionally until the orzo is tender and most of the liquid is absorbed.
Stir in the spinach, parmesan, and lemon juice. Cook for another 2–3 minutes until the spinach wilts.
Taste and adjust seasoning if needed. Serve warm!