The Sydney-born 19-year-old has made the switch to Loftus Road from Palm Beach Soccer Club in his native Australia.
According to the Championship club's official website, Wallen will initially link up with the development squad in West London.
The youngster, who was previously on the books of Premier League side Watford, has agreed a contract until June 2017.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Sunderland | 14 | 9 | 3 | 2 | 23 | 9 | 14 | 30 |
| 2 | Sheffield UnitedSheff Utd | 14 | 9 | 3 | 2 | 18 | 7 | 11 | 28 |
| 3 | Leeds UnitedLeeds | 14 | 7 | 5 | 2 | 22 | 9 | 13 | 26 |
| 4 | Watford | 15 | 8 | 1 | 6 | 23 | 22 | 1 | 25 |
| 5 | Burnley | 14 | 6 | 6 | 2 | 17 | 6 | 11 | 24 |
| 6 | West Bromwich AlbionWest Brom | 14 | 5 | 7 | 2 | 14 | 8 | 6 | 22 |
| 7 | Millwall | 14 | 6 | 4 | 4 | 17 | 12 | 5 | 22 |
| 8 | Middlesbrough | 14 | 6 | 3 | 5 | 18 | 16 | 2 | 21 |
| 9 | Swansea CitySwansea | 14 | 5 | 4 | 5 | 11 | 9 | 2 | 19 |
| 10 | Blackburn RoversBlackburn | 14 | 5 | 4 | 5 | 16 | 16 | 0 | 19 |
| 11 | Bristol City | 14 | 4 | 7 | 3 | 18 | 19 | -1 | 19 |
| 12 | Norwich CityNorwich | 14 | 4 | 6 | 4 | 23 | 20 | 3 | 18 |
| 13 | Derby CountyDerby | 14 | 5 | 3 | 6 | 18 | 18 | 0 | 18 |
| 14 | Stoke CityStoke | 14 | 5 | 3 | 6 | 17 | 18 | -1 | 18 |
| 15 | Sheffield WednesdaySheff Weds | 14 | 5 | 3 | 6 | 17 | 24 | -7 | 18 |
| 16 | Oxford UnitedOxford Utd | 15 | 4 | 5 | 6 | 17 | 18 | -1 | 17 |
| 17 | Coventry CityCoventry | 14 | 4 | 3 | 7 | 18 | 19 | -1 | 15 |
| 18 | Hull City | 14 | 3 | 6 | 5 | 15 | 18 | -3 | 15 |
| 19 | Luton TownLuton | 14 | 4 | 3 | 7 | 16 | 21 | -5 | 15 |
| 20 | Preston North EndPreston | 14 | 3 | 6 | 5 | 14 | 20 | -6 | 15 |
| 21 | Cardiff CityCardiff | 14 | 4 | 3 | 7 | 13 | 20 | -7 | 15 |
| 22 | Plymouth ArgylePlymouth | 14 | 4 | 3 | 7 | 14 | 25 | -11 | 15 |
| 23 | Queens Park RangersQPR | 14 | 1 | 7 | 6 | 12 | 23 | -11 | 10 |
| 24 | Portsmouth | 14 | 1 | 6 | 7 | 13 | 27 | -14 | 9 |
| > Championship Full Table | |||||||||
