Preheat oven to 375°F. Cook ground beef, onion and bell pepper in large skillet on medium heat 5 minutes or until beef is no longer pink, stirring frequently. Drain, if needed. Stir in Seasoning Mix, beans and water. Simmer 5 minutes, stirring occasionally.
Arrange tortilla chips in single layer on 2 lightly greased foil-lined shallow baking pans, overlapping chips if needed to cover pan completely. Top each pan of chips with 1/2 each of the meat mixture and the cheese.
Bake 5 minutes or until cheese is melted. Sprinkle with green onions. Serve immediately with sour cream, if desired.