Toss chicken with 1/2 of the Wish-Bone® Greek Vinaigrette Dressing in large bowl; let stand covered 20 minutes.
Bring broth to a boil over medium heat in 2-quart saucepan. Stir in couscous. Remove from heat and stand covered 5 minutes. Stir in remaining ingredients and set aside.
Remove chicken from marinade. Grill chicken, turning once and basting with marinade, until chicken is thoroughly cooked, about 20 minutes. Discard marinade. Grill lemon until softened and juicy, about about 5 minutes. Squeeze juice of 1 lemon halves over the chicken and let stand covered 5 minutes.
Spoon the couscous mixture onto serving platter, then top with chicken. Garnish with remaining lemons.