The Spaniard was restored to the starting XI on Sunday along with Remy Cabella and Massadio Haidara by Alan Pardew after scoring the winner in each of Newcastle's last two Premier League games.
And the forward - signed from Tenerife in the close-season - once again repaid the faith of his manager by putting Newcastle ahead in the final minute of the first half at The Hawthorns.
West Brom pressed to try and level the scores but were caught on the break by a visiting side that played largely on the counter.
Captain Fabricio Coloccini headed home Newcastle's second and there proved to be no way back for West Brom, who have now won just one of their last six matches.
Newcastle now head into the international break just outside the top six as their outstanding and somewhat surprising renaissance goes on.
The visitors showed early attacking initiative with Paul Dummett heading over and only the crossbar denying Sammy Ameobi's curling left-footed half-volley.
Unsurprisingly it was Saido Berahino, partnered up front by Victor Anichebe as part of two changes by head coach Alan Irvine, that crafted West Brom's first chance.
The striker - called into the England squad for the first time on Thursday after a run of five goals in his previous five league games - forced Newcastle goalkeeper Tim Krul to palm over the bar with a powerful drive from the edge of the area.
West Brom gradually began to dictate the flow of the game but were punished for their failure to create goalscoring opportunities by a superb creative finish from Perez on the stroke of half-time.
The 21-year-old capped off a well-worked Newcastle move by cleverly flicking Daryl Janmaat's diagonal pass through his own legs and past Ben Foster.
Christian Gamboa was brought on for Sebastien Pocognoli by Irvine after half-time but the change had little impact for the hosts, who continued to labour in search of an equaliser.
Their performance going forward was in stark contrast to that of Newcastle, the Tyneside club doubling their advantage with a rare goal from their skipper.
Coloccini headed a pinpoint right-wing cross from Janmaat beyond a helpless Foster, finding the net for the first time in the Premier League since a 1-1 draw with Tottenham in January 2011.
Perez was denied a second as his late volley was tipped over the bar by Foster, whose heroics could not prevent a Newcastle victory that should further silence those calling for Pardew to vacate his post following a poor start to the season that now seems a distant memory.
