1 medium sweet onion, cut into 1/2-inch-thick slices
1/2 cup Hellmann's® or Best Foods® Mediterranean Roasted Garlic & Herb Flavored Mayonnaise, divided
4 ciabatta rolls [or Italian rolls], split
4 ounces sliced mozzarella cheese
Grill eggplant, mushrooms and onion, brushing with 1/4 cup Hellmann's® or Best Foods® Mediterranean Roasted Garlic & Herb Flavored Mayonnaise, turning once, until vegetables are tender, about 10 minutes. Slice mushrooms.
Evenly spread remaining 1/4 cup Mayonnaise on rolls. Arrange eggplant, mushrooms and onion on rolls, then top with cheese.