Combine cheese and olives in a small bowl, stirring until well blended.
Spread about 1 tablespoon cheese mixture evenly over each of 4 bread slices. Divide basil leaves, greens, and bell pepper into fourths; arrange evenly over cheese mixture on each bread slice. Top with remaining 4 bread slices.
Heat a large nonstick skillet over medium heat. Coat pan with cooking spray.
Add sandwiches to pan. Cover with a sheet of foil; top with a heavy skillet. Cook 3 minutes or until lightly browned. Turn sandwiches over; replace foil and skillet. Cook 3 minutes or until golden.