Preheat barbecue grill to a medium heat.
Remove husks and silk threads from the ears or corn.
Remove the top and bottom and the outer layer from the onion and cut into quarters.
Wash the corn, jalapenos, and limes.
Drizzle the onion and corn with olive oil.
Cook corns, jalapenos, limes, and onion quarters on indirect heat for 15 minutes.
Rotate the vegetables over the flames for the last 5 minutes to develop charred edges.
Remove from the heat and cool long enough to handle.
Slice the corn off of the cobs and put in a large mixing bowl.
Slice the jalapenos in half lengthwise and remove the interior ribs and seeds. Finely chop the jalapenos and onion and add to the mixing bowl.
Juice the limes.
Add the remaining ingredients to the bowl and stir to combine.
Garnish with additional cotija cheese, cilantro, and jalapeno slices.