QPR have recruited the 23-year-old striker from Peterborough on a three-and-a-half-year contract.
Former Rangers forward Marsh has suggested on Twitter that Washington will prove to be a good signing for the London outfit.
Really surprised QPR are signing Conor Washington.....— Rodney Marsh (@RodneyMarsh10) January 19, 2016
Conor Washington has a record of delivering the goods...— Rodney Marsh (@RodneyMarsh10) January 19, 201
The former St Ives Town striker will be a replacement for Charlie Austin, who has left QPR for Premier League club Southampton.
Rangers are 15th in the Championship table at the moment with 34 points from 27 matches, 11 points behind Sheffield Wednesday, who are currently sixth and occupy the final playoff spot.