Preheat oven to 350 degrees, Lightly grease a 13x9" baking dish. Heat tortillas - one at a time- in a small skillet over medium-hi heat for 30 seconds on each side or till soft. Place 2 warmed tortillas, side by side, on bottom of prepared baking dish. Spread 2 T. beans over tortilla. Top each with 2 T. cheese & 2 T. green onion (if desired). Repeat each layer until all tortillas are used, completing 2 stacks of 6. Pour remaining enchilada sauce over stacks & sprinkle with additional cheese.
Bake 15-20 minutes. Cut into wedges to serve.