BROWN meat with onions in large nonstick skillet on medium-high heat; drain. ADD seasoning mix and water; mix well. Bring to boil. Simmer on medium-low heat 3 min. DIVIDE lettuce among 4 plates. Top evenly with meat mixture, tomatoes, cheese and crushed chips. Drizzle with dressing. TACO BELL® and Logo are trademarks owned and licensed by Taco Bell Corp.