Fill a large pot of water, add 2 teaspoons of salt and bring to a rolling boil. While the water is heating, heat the grill to 400°F. When it reaches 400°F, clean and oil the grill.
Place the corn into the boiling water and cook for 5 minutes.
Remove with tongs, allow excess water to drain back into the pot and pat with paper towels to dry.
Lightly brush the corn with the olive oil and place on the grill, turning every 30 seconds to a minute, allowing browned spots to form. Total grilling time will be 2-3 minutes.
Remove corn from the grill and allow to cool for 5 minutes.
Remove the corn kernels from the cob with a sharp knife and place into a medium-size mixing bowl.
Add the tomatoes, red onion, avocado, cilantro, serrano, jalapeño, and lime juice, and toss to combine. May be served immediately or covered and refrigerated for a few hours to allow the flavors to blend. Salt to taste prior to serving.