Remove and discard giblets and neck from chicken. Rinse chicken under cold water; pat dry. Trim excess fat. Combine chicken and 3 quarts water in a stockpot; bring to a boil. Add the onion, chopped carrot, chopped celery, and peppercorns; bring to a boil. Partially cover, reduce heat, and simmer 1 hour.
Remove the chicken from broth, reserving broth; cool. Remove chicken from bones; cut meat into bite-size pieces. Strain chicken broth through a sieve over a bowl; discard solids. Add enough water to broth to measure 10 cups; pour broth mixture into stockpot. Add sliced carrot, diced celery, basil, oregano, salt, and bay leaf; bring to a boil. Cover, reduce heat, and simmer 10 minutes. Add chicken and orzo; cook 8 minutes or until pasta is done.