Prepare and bake cornbread mix according to package directions, using an 8-in. square baking dish. Crumble when cool., Mix sour cream, mayonnaise and salad dressing mix until blended. In a separate bowl, combine tomatoes, peppers and 1/2 cup green onions. , In a 3-qt. glass bowl, layer half of each: cornbread, beans, tomato mixture, cheese, bacon, corn and dressing. Repeat layers. Top with remaining green onions. Refrigerate 3 hours.