Following protracted talks, the 18-year-old has moved to London in a deal that will earn Livingston £150,000.
The West Lothian club have also negotiated a sell-on clause with QPR. Donaldson, who was on trial with Manchester United last year, played 29 times for Livingston after making his debut last year. "Coll's worked hard to move his way up through the youth ranks here, so it's always a sad occasion when one of our own moves on," said John McGlynn, the Livingston manager. "But like [Stefan] Scougall, Coll has earned his crack at English football, and we will never stand in the way of ambitious young players."
McGlynn moved swiftly to replace Donaldson by adding the 23-year-old defender Nejc Mevlja from Slovenian side NK Maribor.