Place the first 8 ingredients in a food processor; pulse until tomatoes and olives are coarsely chopped. Cut a pocket horizontally in the thickest part of each chicken breast. Fill with olive mixture; secure with toothpicks., Lightly coat grill rack with cooking oil. Grill chicken, covered, over medium heat or broil 4 in. from heat 8-10 minutes on each side or until a thermometer inserted in stuffing reads 165°. Sprinkle with cheese. Discard toothpicks before serving.