Chop onion and celery, peel and chop carrots, and mince garlic. Heat oil in a large pot over medium-high heat. Add chopped veggies, and cook stirring occasionally until onion is softened, approximately 10 minutes.
Dice chicken and add to pot; season with freshly ground black pepper and salt. Cook stirring frequently until chicken has begun to turn white on the outsides.
Add chicken broth, orzo pasta, worcestershire sauce and herbs (except parsley) Bring to a boil. Reduce heat to medium low and simmer, covered, until orzo is tender but still has some firmness, about 6 to 8 minutes. Stir in the peas and allow them to heat through.
Finish by squeezing the juice of the lemon into the soup. Portion into bowls and garnish with fresh parsley. Enjoy!