Cook orzo according to package directions, omitting salt and fat. Drain.
While orzo cooks, heat a 12-inch nonstick skillet over medium high heat. Coat pan with cooking spray. Add chicken; cook 3 minutes on each side or until done. Remove chicken from pan; cover and keep warm.
Combine Greek seasoning and next 5 ingredients (through salt); set aside.
Recoat pan with cooking spray. Add bell pepper, and sauté 2 minutes. Add onions; sauté 1 minute or until peppers begin to brown. Return chicken to pan. Stir in caper mixture, tossing gently to coat chicken. Spoon chicken mixture over orzo. Serve immediately.