- Prep the ears and submerge the corn in cold water for 10 minutes. Grill the corn for 15-20 minutes at 350-400 degrees F, turning it every 5 minutes to cook evenly. combine the butter, Parmesan, and spices. Let the corn cool for 5 minutes, then peel back the husks. Brush the grilled corn all over with the Mexican butter. Serve hot.