Beattie, who has scored 16 goals for the Hoops will boost the Baggies' options in attack for the coming season.
"Craig will bring qualities to our team that we lacked last season," boss Tony Mowbray told the Baggies' official website.
"He still has room for development in his game and he will hopefully progress here as a footballer.
"Craig has shown a determination and desire to do well in England and already has Champions League and international experience.
"His main attributes are playing on the shoulder of the last defender.
"He utilises his pace and power well and manages to get in behind defences to score goals."