Combine mustard and 2 tablespoons vinaigrette. Grill bratwurst and corn, covered, over medium heat for 15-20 minutes or until meat is no longer pink and corn is tender, turning frequently and basting with mustard mixture.
Cut corn from cobs. In a small bowl, combine the corn, peppers, green onion and remaining vinaigrette. Serve brats in buns with corn relish.