Lightly brush the chicken breast halves with 1 tablespoon of the vinaigrette and set aside.
Coat a grill pan or grill rack with cooking spray and place over medium-high heat until hot. Coat the pepper and onion with cooking spray and cook 4 to 6 minutes on each side or until just tender and slightly charred. Place on cutting board to cool slightly.
Cook chicken 4 to 5 minutes on each side or until no longer pink in center.
Meanwhile, chop the cooked pepper and onion and place in a medium bowl with the olives, rosemary and remaining vinaigrette. Toss gently until well blended. Serve over chicken.