Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Sprinkle chicken with salt and pepper. Add chicken to pan; cook 5 minutes on each side or until done. Cut into 1/2-inch slices.
Combine greens, tomatoes, avocado, and onions in a large bowl. Drizzle greens mixture with dressing; toss gently to coat. Arrange about 2 cups greens mixture on each of 4 salad plates. Top each serving with 4 ounces chicken, 1 1/2 teaspoons cheese, and about 1/2 teaspoon bacon.