1. Combine mayonnaise, vinegar, and pepper; set aside.
2. Heat a large nonstick skillet over medium-high heat; coat pan with cooking spray. Cook bacon until crisp (5-6 minutes), stirring occasionally. Remove bacon from skillet; pat with paper towels.
3. Carefully separate 8 large leaves from lettuce head (do not tear) to use as wraps; reserve remaining lettuce for another use. Place 1 lettuce leaf inside another to create 4 (2-layered) wraps; fill with about 1/4 cup turkey breast, 1/4 of the cubed tomato (about 1/4 cup), 1/4 cup cubed avocado, and 2 tablespoons diced onion. Drizzle with 1 tablespoon reserved dressing; top with 1/4 of the crisped bacon and 2 teaspoons crumbled blue cheese.