Preheat grill to medium-high heat (350- 400 degrees F). Brush corn with oil and season with salt and pepper. Grill, turning occasionally until lightly charred (about 10-15 minutes). When corn is cool enough to handle remove kernels from cob.
In a large bowl, combine all the ingredients for the vinaigrette. Add corn, tomatoes, avocado, bell pepper, and red onion. Gently toss to coat. Serve immediately or store in the refrigerator for up to 1 day. I was able to keep this in the fridge for 2 days. Be sure to press plastic wrap across the surface of the salad to help prevent the avocado from browning.