Preheat the grill to high heat.
Heat a large nonstick skillet over medium heat. Add bacon to pan; cook 8 minutes or until crisp, tossing occasionally to curl. Drain bacon on paper towels.
Combine buttermilk and next 5 ingredients (through garlic), stirring with a whisk.
Stir in 1/4 teaspoon pepper.
Coat corn with cooking spray.
Place corn on grill rack; grill 8 minutes or until well marked, turning occasionally. Remove from grill; cool slightly.
Cut corn kernels from cobs.
Sprinkle tomato slices evenly with salt.
Alternate layers of tomato and avocado on each of 4 plates.
Scatter corn evenly onto plates.
Drizzle each tomato stack with about 1 1/2 tablespoons dressing and 1 teaspoon oil.
Sprinkle remaining 1/4 teaspoon black pepper over salads; top each salad with 1 bacon piece.