In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for about 5 minutes until translucent. Stir in the minced garlic, carrots, and celery, cooking for an additional 3-4 minutes until the vegetables are tender.

Sprinkle in the dried oregano and thyme, stirring to combine. Add the chicken breasts to the pot and pour in the chicken broth. Bring the mixture to a boil, then reduce the heat and let it simmer for 15-20 minutes until the chicken is cooked through.

Remove the chicken from the pot and shred it using two forks. Return the shredded chicken to the pot.

Stir in the uncooked orzo pasta and let it cook for about 8-10 minutes or until al dente.

Add the chopped spinach and lemon juice, stirring until the spinach wilts. Season with salt and pepper to taste.

Serve hot, garnished with fresh parsley.