The young midfielder - whose passing ability is notably one of his strongest traits - joins the Clarets for the remainder of the season, adding further quality to Rod Stringer’s midfield department.
Having been born in Sydney, Wallen signed for the R’s as a 19-year-old from Palm Beach Soccer Club.
The youngster signed a one-year deal after having his 2016/17 season disrupted by a long-term injury, making just five appearances for the under-23 side, and his contract at Loftus Road expires this summer.