Sprinkle 1/4 teaspoon pepper and salt evenly over chicken.
Heat oil in a large nonstick skillet coated with cooking spray over medium heat. Add chicken; cook 5 minutes on each side or until browned. Remove chicken from pan; keep warm. Add onion to pan; sauté 5 minutes or until tender. Add garlic; sauté 1 minute. Add 1/2 cup broth and next 3 ingredients. Return chicken to pan; bring to a boil. Cover, reduce heat, and simmer 30 minutes or until chicken is done. Stir in remaining 1/4 teaspoon pepper and parsley.
Meanwhile, bring remaining 1 1/2 cups chicken broth to a boil in a medium saucepan; gradually stir in couscous. Remove from heat; cover and let stand 5 minutes. Fluff with a fork. Serve chicken and sauce over couscous.