Bring vinegar to a boil in 2-quart saucepan. Reduce heat; simmer, uncovered, 9 to 10 minutes or until reduced to 1/3 cup. Set aside.
Meanwhile lightly shape Ground Beef into eight 1/2-inch thick patties.
Brush polenta slices with oil. Place patties in center of grid over medium, ash-covered coals. Grill burger patties, uncovered, 11 to 12 minutes (over medium heat on preheated gas grill, covered, 9 to 10 minutes), until instant-read thermometer inserted horizontally into center registers 160°F, turning burgers occasionally and basting with 2 tablespoons reduced vinegar after turning. Arrange polenta around patties; grill 11 to 12 minutes (for gas, grill 9 to 10 minutes) or until heated through, turning once. Season burgers with salt and pepper, as desired.
For each serving, layer 1 each polenta slice, burger patty, mozzarella slice and tomato slice. Drizzle with remaining vinegar and sprinkle with basil, as desired.
Nutrition information per serving: 324 Calories; 150.3 kcal Calories from fat; 16.7 g Total Fat; 7 g Saturated Fat; 0.2 g Trans Fat; 0.8 g Polyunsaturated Fat; 5 g Monounsaturated Fat; 83 mg Cholesterol; 217 mg Sodium; 17 g Total Carbohydrate; 0.4 g Dietary Fiber; 4 g Total Sugars; 26 g Protein; 0 g Added Sugars; 122.7 mg Calcium; 3.1 mg Iron; 400 mg Potassium; 0 mcg Vitamin D; 0.2 mg Riboflavin; 5.6 mg NE Niacin; 0.3 mg Vitamin B6; 2.1 mcg Vitamin B12; 193 mg Phosphorus; 5 mg Zinc; 17.4 mcg Selenium; 74 mg Choline;