Heat oven to 400 degrees. Cook meat and onion in a large skillet over medium heat until browned and crumbly; drain. Stir in beans. Place chips on a large, foiled-lined, rimmed baking sheet. Distribute meat mixture and cheese evenly over chips. Bake 10 minutes or until cheese is melted. Divide evenly onto individual serving plates. Top with desired amounts of lettuce, sour cream, olives, and tomatoes