The 23-year-old has scored six goals in 25 games since initially joining Wycombe on loan in July and has now signed a three-and-a-half-year deal.
Harriman, who is equally capable in defence or midfield, made just three first-team appearances for the R's.
"He's got everything you want from a professional," boss Gareth Ainsworth told the club website.
"He gives his all, he's got bags of ability and he's a great character to have around the club.
"To be able to keep him here is a fantastic piece of business and I'm grateful for the support of the board who have enabled me to make Michael a permanent signing."
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The Child Exploitation and Online Protection Centre, now part of the National Crime Agency, took more than a year to pass the details on to police.
Canadian police sent files to CEOP on about 2,000 men, including Myles Bradbury, convicted in September of abusing boys at a hospital until 2013.
NCA head Keith Bristow told MPs he was sorry if children had been put at risk.
Information on the men was sent by Toronto Police in July 2012, as part of an international investigation, Operation Spade, into suspected paedophiles.
But it was not passed on to police forces until more than 12 months later in November 2013.
The BBC has obtained figures from several police forces suggesting they have arrested only about a third of the names they were given.
And so far just 6% have been charged, including teachers and nursery workers.
West Yorkshire Police, which received the names of 60 people a year ago, had made no arrests a week ago but in the last few days has arrested 24 men
A spokesman for the force said the arrests were very recent and no-one had yet been charged.
Mr Bristow told the home affairs select committee: "Sitting on data for the period of time between July 2012 and November 2013, that could have led to children being protected or safeguarded, seems to me whether it's systemic or it's down to individuals - and there are certainly some systemic issues that we need to work through - that's not in the spirit of what we stand for.
"I'm sorry if that's led to harm to children or exposing them to risk because that's not what we stand for."
Mr Bristow told the committee: "We are sat on a daily basis on top of significant risk because of the sheer volume of images and the different methods of offending by people who have a sexual interest in children.
"And we have a problem - not just NCA, not just law enforcement, not just government - we as a society have a problem with the number of people in the UK who access these horrible images or paying for children to be abused online."
Police watchdog the IPCC has written to every chief constable to see if information from the Canadian investigation has been mishandled.
Det Insp Jim Foy, of another of the forces, West Midlands Police, said: "In November 2013, we received 58 packages from the National Crime Agency (NCA) in connection with Operation Spade.
"After an initial assessment of the information provided, 30 were found to be no longer for our attention as either the suspects were already under investigation, were deceased or had moved away from the West Midlands Force area.
"Of the remaining 28 referrals, four people have already been charged with offences. Two are awaiting charging advice from the Crown Prosecution Service (CPS) and 16 have been arrested and are currently on police bail.
"No further action was required in six of the packages: we found no evidence of any offences in five of the referrals and one of the cases involved a man with serious mental health issues."
League Two side Wycombe Wanderers have signed utility man Michael Harriman from QPR for an undisclosed fee.
[NEXT_CONCEPT]
A law enforcement chief has apologised for delays in acting on information about possible British paedophiles.