Hoilett is one of nine QPR players whose contracts expire in the summer, and the club are yet to offer the wide man a new deal.
Hoilett is reportedly on a £40,000-per-week deal at Loftus Road currently, and QPR simply cannot afford to offer him such terms again without top level football on offer.
Rangers are believed to be open to giving Hoilett a cheaper deal, but the winger is loathed to take a reduced deal.
As a result, Besiktas and Monchengladbach have apparently been alerted to his potential availability.
The pair believe the Hoilett could enhance the quality of their squads, even though he has had an inconsistent campaign this season.
Hoilett started the season completely out of favour, but under Neil Warnock and, more recently, Jimmy Floyd Hasselbaink he has played a key role.
Hoilett moved to QPR in 2012, and he has racked up 110 league appearances for the London side to date.