In a large pot, heat the olive oil over medium heat. Add the diced onion, carrots, and celery. Sauté for about 5 minutes until the vegetables start to soften.
Add the minced garlic to the pot and cook for an additional 1 minute until fragrant.
Pour in the chicken broth and bring it to a boil. Reduce the heat to low and let it simmer for about 10 minutes to allow the flavors to meld together.
Add the cooked chicken to the pot and stir to combine.
Stir in the orzo pasta, lemon juice, lemon zest, and dried thyme. Let the soup simmer for another 10- 12 minutes until the orzo is cooked al dente.
Season the soup with salt and black pepper to taste.
Remove the pot from the heat. Taste the soup and adjust the lemon juice or seasoning if desired.
Ladle the lemon chicken orzo soup into bowls and garnish with chopped fresh parsley.
Serve the soup hot and enjoy!