Cook the orzo according to the directions on the box. Cut the roasted/cooked chicken into bite size pieces.
Prepare the cucumber, green onions, green pepper, and celery. When completed put them in a medium bowl.
Prepare the dressing in a small food processor. Add the garlic, basil, oregano, and parsley. Pulse until the garlic and herbs are finely chopped.
Add the vinegar and Dijon mustard. Pulse until combined. Slowly add the olive oil. Mix until well blended.
Add the chicken and orzo to the bowl with the vegetables. Toss until well combined. Add the dressing and toss until all is coated. Chill before serving.