BURGERS: MIX all ingredients; shape into 32 patties (or into 2 patties for trial recipe).
FOR each serving: Grill 1 burger on medium-high heat 5 min. or until medium (160ºF) or desired doneness, turning after 3 min. Meanwhile, toast cut sides of 1 bun on grill 15 sec. or until golden brown.
SPREAD 2 Tbsp. dressing evenly onto cut sides of bun.
PLACE 1 lettuce leaf on bottom half of bun; top with 2 tomato slices, 2 onion rings, 1 burger, 2 cheese slices, 2 Tbsp. vegetable blend, 2 avocado slices and 2 tsp. steak sauce. Cover with top bun.