Divide tomato slices evenly among 4 bread slices; sprinkle evenly with salt and pepper. Sprinkle cheese evenly over tomatoes. Arrange basil leaves evenly over cheese, and top with remaining 4 bread slices. Drizzle 1 teaspoon olive oil over top of each sandwich, and coat with cooking spray.
Place a grill pan or large nonstick skillet over medium-high heat until hot. Place sandwiches, oil sides down, in pan. Drizzle 1 teaspoon oil over top of each sandwich, and coat with cooking spray. Place a piece of foil over sandwiches in pan; place a heavy skillet on top of foil to press sandwiches. Cook 2 minutes or until golden brown. Turn sandwiches over; replace foil and heavy skillet. Cook 2 minutes or until golden brown. Serve immediately.