Light a grill. Brush the corn with oil and grill over moderate heat until lightly charred, 8 minutes. Cut the kernels from the cob.
In a bowl, mix 2 tablespoons of oil with the vinegar. Fold in the corn, tomatoes, chile and cilantro and season with salt and pepper. Top the bread with the sliced avocado, tomato salad and pickled onions and serve.