Set oven control to broil. Spray broiler pan rack with cooking spray. Starting at thickest edge of each chicken breast, cut horizontally almost to opposite side. Open cut chicken breast so it’s an even thickness.
In small bowl, mix oil and lemon juice. Drizzle over both sides of chicken breasts. Sprinkle both sides with lemon-and-pepper seasoning. Place on rack in broiler pan.
Broil with tops 4 inches from heat about 10 minutes, turning once, until chicken is no longer pink in center. Top with olives and lemon slices during last 2 minutes of broiling.