Brown ground beef together with onion and green pepper in a large, nonstick skillet on medium-high heat. Drain fat
Stir in taco seasoning, beans, chopped tomatoes, and frozen corn
Bring to boil. Reduce heat to low; simmer 5 min.
Spoon mixture into a 2-qt. baking dish. Sprinkle with cheese and crushed tortilla chips
Bake until cheese is melted and the mixture is bubbly about 10 min. Serve hot garnished with sliced scallions