Place peppers on hot grill about fifteen minutes until charred. Place in glass bowl and cover with saran wrap. Soak corn and husks in water for 10 minutes. Grill corn and husks, rotating every 10 minutes, for 25 minutes. Peel off outer layer of peppers and slice in half. Scrape out seeds and veins. Mince peppers and place in bowl. Husk corn and shave off kernels into bowl. Mix peppers, corn, and feta into bowl; add mayo, salt, and pepper to taste.