Cook orzo in saucepan following package directions.
Meanwhile, coat chicken with dressing in plastic food-storage bag. Remove from bag to broiler-pan rack.
Broil 3 to 4 minutes on each side or until internal temperature registers 170°F. Remove to plate; keep warm.
Meanwhile, heat oil in large skillet over medium-high heat. Add onion and garlic; saute 3 minutes or until softened. Add tomatoes; cook 3 minutes. Add olives, salt and pepper; cook 1 minute to heat through. Toss with orzo in saucepan.
Spoon orzo onto platter. Arrange chicken on top.