Spray both sides of zucchini rounds lightly with nonstick cooking spray. Sprinkle with salt and pepper. Broil or grill the zucchini rounds (grill pan set to medium-high) for 2 minutes on each side.
Place cooked zucchini rounds on a large lined baking sheet. Top with small amounts of sauce, cheese and pepperoni pieces, if desired. Broil for an additional 1-3 minutes, or until cheese is melted, careful not to burn. Sprinkle with Italian seasoning and serve warm.