FREE highlights of Albion's pulsating 4-2 victory over Bristol City at The Hawthorns.
The on-loan forward showed pace, power and composure beyond his 20 years to set up Dwight Gayle and Jay Rodriguez, who had earlier opened the scoring from the penalty spot, as the Baggies took firm control courtesy of three goals inside 12 first-half minutes.
Having already claimed two assists, Barnes got the goal he deserved in the 63rd minute, restoring Albion's three-goal advantage after Lloyd Kelly had momentarily reduced the arrears.
City substitute Famara Diedhiou curled in a second for the visitors but it proved merely a consolation in what was a six-goal thriller, Albion taking all three Sky Bet Championship points to register a fifth successive win on home soil.
Attacking trio Barnes, Gayle and Rodriguez now boast 12 league goals between them, with Millwall next up on Saturday as Albion look to continue their momentum.
Fit-again Kieran Gibbs returned in place of Conor Townsend while Gareth Barry came in for Chris Brunt, with Craig Dawson taking over the captain's armband.
The Robins, having won their previous four matches on the spin, flew out of the traps and Sam Johnstone was called into action three times inside the opening 90 seconds.
Yet the Baggies keeper saved his best save for the seventh minute, quick off his line to punch clear Andreas Weimann's attempted lob when clean through.
And it proved crucial as Albion took the lead in the 16th minute, Rodriguez drilling home from the penalty spot after Gayle had been tripped by Adam Webster.
Robins stopper Niki Maenpaa got down well to keep out Dawson's header but he could do nothing to stop Albion's second in the 24th minute.
Barnes embarked on a surging run from deep and laid the ball into the path of Gayle, who cut on to his left foot and dispatched past Maenpaa.
Barnes was at it again just minutes later as he held off his man and broke down the left, squaring for Rodriguez to slot home from close range.
The Baggies were firmly in control inside the opening half an hour and Barnes saw his free-kick sail narrowly over the crossbar shortly before the break.
Gayle drilled over soon after the restart as Albion threatened a fourth goal while Johnstone tipped over Josh Brownhill's free-kick at the other end.
City applied pressure as they searched for a route back into the game and, shortly after Dawson had sent the ball against his own post, Watkins flicked in to make it 3-1.
However, the Baggies restored their three-goal advantage almost immediately as Gayle turned provider to set up Barnes, who applied the perfect finish to get in on the act and register his name on the scoresheet.
City sub Diedhiou found the net with a well-placed effort in the 68th minute as the battling away side refused to give up hope.
But Darren Moore's charges held firm and, with Wes Hoolahan handed his debut, registered victory in front of the home faithful.
ALBION: Johnstone, Dawson (c), Hegazi, Bartley, Phillips, Barry (Field 87), Livermore, Gibbs, Barnes, Rodriguez (Robson-Kanu 80), Gayle (Hoolahan 74).
Subs: Myhill, Mears, Adarabioyo, Brunt.