Cook ground beef and onions in a dutch oven over medium heat, stirring until beef crumbles and is no longer pink, drain. Add beans, corn, tomato sauce and seasoning mix, stir until blended. Simmer over medium heat for 10 minutes.
Pour half of the beef mixture into a lightly greased 13x9" baking pan. Top with 1 1/2 cups each of cheese and crushed chips, top with remaining beef mixture and remaining cheese and chips. Bake at 350 degrees for 25-30 minutes or until bubble and golden. Sprinkle with chopped tomatoes and green onions.