In a medium bowl, mix together the chili powder, oregano, onion powder, cayenne pepper, garlic powder, salt, and pepper. Blend in the softened butter. Apply this mixture to each ear of corn, and place each ear onto a piece of aluminum foil big enough to wrap the corn. Wrap like a burrito, and twist the ends to close.
Place wrapped corn on the preheated grill, and cook 20 to 30 minutes, until tender when poked with a fork. Turn corn occasionally during cooking.