Polenta Stack With Navy Bean Salad

Vegetable oil cooking spray

each) navy beans, rinsed and drained

plum tomatoes, chopped

basil, chopped, plus 15 leaves for garnish

crumbled feta, divided

tube (18 ounces) prepared polenta, cut into 16 slices

zucchini, cut into 1/4-inch slices

bottles (7 ounces each) roasted red peppers, drained