Trim excess fat from roast; combine dry soup mix and onion on a sheet of aluminum foil or wax paper. Roll roast in mixture to coat well. Place coated roast in a crockpot, pour wine or water over; cover. Cook on Medium for 8 hours, turning after 4 hours, if possible, or on High for 4 hours, turning after 2 hours if possible, or until meat is tender.
Serve with mashed potatoes and buttered green beans.