In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté until translucent, about 5 minutes. Stir in the minced garlic and cook for an additional minute until fragrant.

Add the sliced carrots and celery to the pot, cooking for another 5 minutes until they begin to soften.

Pour in the chicken broth and bring to a boil. Add the chicken breasts, orzo pasta, oregano, thyme, salt, and pepper. Reduce heat to a simmer and cook for 15-20 minutes, or 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 lemon juice and fresh spinach, cooking for an additional 2-3 minutes until the spinach is wilted.

Taste and adjust seasoning if necessary. Serve hot, garnished with chopped fresh parsley.