1. Preheat the grill to high heat.
2. 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.
3. Combine buttermilk and next 5 ingredients (through garlic), stirring with a whisk. Stir in 1/4 teaspoon pepper.
4. 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.
5. 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.