Chop two tomatoes; cut remaining tomatoes into wedges. In a large salad bowl, toss the lettuce, tortilla chips, cheese, beans, avocado and chopped tomatoes; set aside.
In a large microwave-safe bowl, combine hamburger mix and taco sauce. Cover and microwave on high for 2-3 minutes or until heated through. Spoon over salad; toss gently. Top with tomato wedges and onions. Serve with dressing. Yield: 10 servings.