Ensure the corn is young by pressing a fingernail into a grain, if the liquid inside is milky then use this method, otherwise use the other method for corn. Don’t grill very mature corn.
Young Corn: Pull back the husk on the corn and remove the silk. Brush the cob with butter and re-wrap the husk around it. Cover with a 10cm wide band of foil. Grill turning frequently, until all sides are very hot and the exposed husks char, about 5-10 minutes.
Corn: De-husk the corn, brush with butter and seal well in foil. Cook on the grill rack turning frequently until cooked. Alternatively, precook the corn and reheat in foil with butter.