Grill corn: Preheat grill to medium-high heat. Brush corn with oil and season generously with salt and pepper. Grill corn, covered, for 10-15 minutes or until charred and browned, turning frequently. Remove corn from grill and allow to cool enough to handle. Slice kernels off the cobs.
Make the dressing: In a blender or the bowl of a food processor, combine all the ingredients for the dressing along with 1/4 teaspoon of both kosher salt and fresh ground pepper. Blend, or process until smooth. Taste and adjust for seasoning with salt and pepper. If a thinner dressing is desired, add in more buttermilk one tablespoon at a time until desired consistency is achieved.
Assemble the salad: Add all of the ingredients for the salad, including the grilled corn, to a large bowl. Toss to combine and season with salt and pepper. Drizzle with dressing and enjoy!