The centre-back departs Anfield as a winner after calling time on his career, as a first-half thunderbolt from the Brazilian claims victory for Brendan Rodgers side
The game, which was the last in a red jersey for Jamie Carragher was controlled by the Reds throughout, with Coutinho the tormentor-in-chief of the relegated west London outfit.
The home side made a trio of changes, as Sebastian Coates, Andre Wisdom and Jonjo Shelvey dropped out, to be replaced by Martin Skrtel, Jose Enrique and 17-year-old Jordan Ibe who was making his debut for the Anfield side.
Harry Redknapp too, made three changes from the side that fell to defeat at home to Newcastle, with Michael Harriman, Shaun Derry and Park Ji-Sung all starting, with Jose Bosingwa, Jermaine Jenas and Junior Hoilett all missing out.
Liverpool thought they had taken an early lead with only two minutes gone, as Coutinho headed a corner from Stewart Downing towards goal, but Robert Green managed to somehow clear before the ball crossed the line.
The visitors were protesting for a penalty a couple of minutes later, as Loic Remy went down inside the Liverpool penalty area under a challenge from Lucas, but referee Martin Atkinson waved away the claims.
Brendan Rodgers' side controlled the pace of the game, with Coutinho once again coming close as he came in from the left hand side, but his effort at goal took a deflection and ultimately went out for a corner.
Coutinho did eventually get on the scoresheet with 23 minutes gone, as young Ibe beat a couple of QPR defenders, before setting up the Brazilian, who unleashed a strike from almost 25-yards out which beat Green.
Just before the half-time break Liverpool had another chance to double their advantage as Enrique beat a couple of visiting defenders, but his effort towards goal was poor.
Coutinho helped to set-up the first chance of the second half for the home side, passing to Enrique, whose effort was saved at the second attempt by Green.
QPR rarely threatened the Liverpool, but they managed to work Pepe Reina just before the hour mark, as Remy raced towards goal, but the Spanish keeper done well to deny him.
A couple of minutes later the home support almost got the moment they were hoping for, as Carragher picked up the ball 30 yards out and unleashed a stunning effort which smacked off of Green's post.
The follow-up to that move saw both Downing and Daniel Sturridge attempt to smash crosses across the danger area, but on both occasions no-one was available to finish the move off and double the lead.
As the game entered the last quarter of an hour, Liverpool continued to press, with the ball being lifted by Jordan Henderson towards Suso, but the young Spaniard couldn't find the finish.
With five minutes left in the game Rodgers decided to bring off Carragher, who received a standing ovation for the Anfield faithful as the saw out a comfortable victory.