Grease 6 quart crockpot with cooking spray. Set aside.
In a very large mixing bowl combine onion, celery, mushrooms, apples, stuffing, rosemary, nutmeg, sage, thyme, salt, and pepper.
Pour melted butter and vegetable broth over the stuffing and mix again.
Pour stuffing into the prepared crockpot (it will be very full).
Cover and cook on LOW for 4 hours.
Taste and re-season, if necessary, and serve!
