Prepare a grill for medium heat.
Throw the corn (in the husk) on the grill and grill, turning occasionally, until the corn is cooked and the husks have char marks, 10 to 15 minutes. Strip the husks off the corn.
While the corn is cooking, add the butter, garlic powder, smoked paprika and some salt and pepper to a small bowl and mix well.
Spread the butter mixture generously on the corn and sprinkle with the feta cheese.