I found this recipe in Martha Stewart's Everyday magazine, and it is also listed on many blogs (see address below). It is a good, quick, and healthy meal.
Full recipe found at and picture curtosey of:
My husband wanted meat in it (even though I was going for a Meatless Monday), so adding to the directions, I cooked up the mushrooms and beans, browned 1 lb. ground beef, then mixed half of the veggie mix with meat(next time, I will include some taco seasoning in with the beef). I did half veggie and half with meat in the casserole dish.
Served alongside was: homemade guacamole, sour cream, and extra salsa. I also roasted up some corn in the oven with a quick and easy recipe by Gina at Skinny Taste - http://www.skinnytaste.com/2011/08/roasted-corn-with-cilantro-butter.html