Grill corn, covered, over medium heat 10-12 minutes or until lightly browned and tender, turning occasionally. Cool slightly. Cut corn from cob.
Arrange tomato slices on a large serving platter. Sprinkle with ½ teaspoon salt and ¼ teaspoon pepper. Top with avocado slices.
Whisk together the oil, vinegar, basil and remaining ¼ teaspoon salt and ¼ teaspoon pepper; drizzle half over tomatoes and avocado.
Top with grilled corn and feta; drizzle remaining dressing over top. Garnish with additional chopped basil.
