Mame Biram Diouf (twice), Ryan Nelsen, Gael Givet and El-Hadji Diouf could all have given their side a comfortable lead but it was left to the 20-year-old Hoilett to show them how it should be done with a shot from the edge of the penalty area late in the second half.
The sparse crowd of 10,284 - 14,238 fewer than the one which witnessed the midweek Premier League victory over Liverpool - was given plenty of goalmouth action but had to wait until 14 minutes from time for the decisive finish.
It took Rovers just 51 seconds to carve out their first chance when Mame Biram Diouf fired across Paddy Kenny but wide of the far post.
There then followed almost a procession of chances for the home side - exactly the type which on Wednesday they had buried against the Merseysiders.
At the heart of it all was Morten Gamst Pedersen, who was the major creative force from central midfield.
When he was not swinging in tempting crosses or firing in free-kicks he was prompting and probing in an attempt to find the one pass which would break down QPR's defence.
Hoilett, man of the match against Liverpool, also put in another positive display and eventually provided the killer blow which had been so lacking in everything previously.
Rovers should have been well out of sight by that point, however, as they had enough opportunities in the first half alone to put the result beyond doubt.
Nelsen headed wide Pedersen's inswinging free-kick before only the brilliance of Kenny kept the score goalless at half-time.
Pedersen's 18th-minute cross from the right brilliantly picked out Mame Biram Diouf but the Senegalese striker saw his header expertly tipped over.
Seconds later the goalkeeper produced an identical save to deny Givet, who had deflected Pedersen's cross goalwards.
It was the Frenchman's last contribution as he soon departed on a stretcher after a collision with Jamie Mackie which also saw the QPR forward carried off after lengthy treatment.
When the action resumed Pedersen was quickly back into his stride, teeing up El-Hadji Diouf on the edge of the penalty area only for him to sidefoot over.
QPR had limited opportunities of their own but although they were infrequent they were decent chances.
Before he was injured Mackie's shot beat Mark Bunn only for Nelsen to clear off the line while Petter Vaagan Moen's fizzing 40-yard free-kick in first-half added time was tipped onto the crossbar by Bunn.
Mame Biram Diouf should have put his side ahead on the hour after getting around the back of the QPR defence to latch on to Pedersen's free-kick.
However, his attempt at controlling the ball on his thigh was poor and it shot away from him and off the pitch close to the post.
Hoilett was closer as his shot, after a weaving run along the edge of the penalty area was deflected just over by Clint Hill.
El-Hadji Diouf then drove into the side-netting as Rovers began to turn up the pressure, which ultimately resulted in Hoilett's winner.
The breakthrough finally came in the 76th minute when El-Hadji Diouf cut in from the left, beat a couple of defenders and squared the ball to Hoilett on the edge of the penalty area.
The 20-year-old's perfectly-aimed shot beat Kenny's dive and nestled in the corner of the net.
Jason Roberts, who came on as a substitute at half-time, should have made the result safe moments later but headed wide unmarked from Josh Morris' cross to the near post.
With six minutes to go Kaspars Gorkss' header hit the crossbar - the second time the visitors had been denied by the woodwork - and it was obvious their luck was not in.