1. Combine first 4 ingredients in a small bowl.
2. Divide beef into 4 equal portions, gently shaping each into a 1/2-inch-thick patty. Press a nickel-sized indentation in the center of each patty; sprinkle patties evenly with salt and pepper. Heat a large skillet or grill pan over medium-high heat. Coat pan with cooking spray. Add patties to pan; cook 3 minutes on each side. Top each patty with 1 cheese slice; cook 2 minutes or until cheese melts and patties are desired degree of doneness.
3. Place 1 lettuce leaf on bottom half of each hamburger bun; top with 1 patty, 1 onion slice, 2 tomato slices, about 2 avocado slices, 2 pickle chips, about 1 1/2 tablespoons sauce, and top half of bun.