Place the mushrooms and frozen pearled onions in the base of a 6 quart or larger slow cooker withthe water. Place the beef roast on top and season with the rosemary, thyme, salt and pepper.
Set the slow cooker on low and cook for 8 hours. If you wish to eat earlier in the day, you can cookon high for 4 to 5 hours.
Once cooked, remove the meat and place it on the serving platter. Slice and then spoon themushroom and onion broth over the meat on the serving platter.
You could whisk in a little flour or gluten free flour blend to make a gravy if you'd like!
Serve Beef Roast with Mushrooms and Pearled Onions as holiday main dish.