1. In small saucepan cook vinegar over low heat about 5 minutes or until reduced to 2 tablespoons and syrupy. Set aside.
2. In small bowl stir together olive oil and garlic. Brush bell peppers, zucchini and eggplant with olive oil mixture.
3. Grill peppers and zucchini over medium heat for 5 minutes, turning occasionally. Add burgers and eggplant to grill. Grill for 4 to 6 minutes more or until burgers are heated through and vegetables are tender, turning occasionally. Remove from grill. Cut vegetables into 3/4- to 1-inch pieces.
4. To serve, spoon vegetables on burgers. Drizzle with balsamic vinegar.