Preheat oven at 350 degrees. Coat a casserole dish (about 11 x 8, a 3-quart rectangle dish) with cooking spray.
In a large pan melt the reduced-fat butter. Add the onions, mushrooms, leeks, celery, and sauté the vegetables until soft and transparent.
In a large bowl, add the cubed stuffing, vegetables, chicken broth, cranberries, sage, and pepper. Mix well.
Spread stuffing into a casserole dish.
Cover and bake for 35-40 minutes until piping hot.