Heat grill. Fold four 18-inch-long pieces of foil in half; unfold and coat inside with cooking spray. Combine beans, tomatoes, chopped basil and 5 ounces feta in a bowl. Place 1/4 of bean mixture in center of 1 half of each piece of foil. Working 1 packet at a time, place 4 slices polenta in an overlapping circle over beans. Top with 1/4 of zucchini slices, 1/4 of red peppers and 1/4 of remaining 5 ounces feta. Fold foil to close and crimp edges to seal packets; place on grill; close lid; cook until packets are fully puffed, 10 minutes. Carefully cut foil to open and garnish with basil leaves. Serve.