The 23-year-old is currently on loan at Alcorcon but he has revealed to Daily Record that he would consider returning to Scotland with Celtic or Rangers.
The player has confirmed that his family are Rangers fans but he would consider a move to rivals Celtic as well.
Harper has claimed that Rangers are back challenging for the top honours under Steven Gerrard and they are a mythical club.
He said: “People in Spain don’t know how important both teams in Glasgow are. Both Celtic and Rangers are mythical clubs – 60,000 fans go to the games.