Brush all sides of corn with oil. Grill, covered, over medium heat, turning occasionally, until tender and lightly browned, 10-12 minutes. Remove from grill; cool slightly.
Meanwhile, in a small bowl, mix mayonnaise, garlic powder and pepper. Cut each ear of corn into thirds. Insert one corncob holder into each piece. Spread corn with mayonnaise mixture; sprinkle with cheese, seafood seasoning and cilantro. If desired, serve with lime wedges.