1. Brush both sides of eggplant slices with olive oil. Divide mozzarella, tomato, and basil among 4 eggplant slices. Sprinkle with salt and pepper; top with remaining 4 eggplant slices.
2. Place eggplant sandwiches and lemon halves on greased grill rack. Grill over medium-high heat (350° to 400°) for 3 to 4 minutes on each side or until cheese melts and eggplant is cooked through. Serve immediately with grilled lemon halves.