Place frozen meatballs in a slow cooker.
Add Worcestershire sauce, sliced mushrooms, water, powdered onion, powdered garlic, and brown gravy mix to the slow cooker.
Stir well to combine all ingredients.
Cover and cook on low for 4-6 hours or on high for 2-3 hours, until meatballs are heated through and flavors are combined.
Serve hot and enjoy!