Preheat the grill to medium-high heat.
In a small bowl, combine the mayonnaise, lime juice, and cumin. Set aside.
Lightly oil the grill grates and place the cobs on the grill. Grill for 7-9 minutes, or until hot and slightly charred all over.
After removing the corn from the grill, immediately roll the cobs in the melted butter, then in the mayo mixture.
Sprinkle the cotija cheese and chili powder over the cobs.
Garnish with chopped cilantro and serve with lime wedges.