Danish forward Osula, starting for the first time since the opening day of the season, met Jacob Murphy's terrific curling cross to stab home the opener for the visitors just after the break.

And just before the hour, Barnes swept home Amar Dedić's cutback to double the Magpies' advantage at Selhurst Park and make sure of the points on a satisfying away day for the travelling hordes.

Matthias Jaissle made five changes to his side for the trip to South London, with Dan Burn, Fabian Schär, Dedić, Murphy and Osula all coming into the line-up.

But Palace had the best early chance, with goalkeeper Lukáš Horníček having to react quickly to smother Jean-Philippe Mateta's close range effort.

The Eagles' French frontman pulled another shot wide from range before Daichi Kamada tumbled under the challenge of Schär in the box. Referee Paul Tierney, however, was unmoved.

At the other end, the Magpies looked to carve out their first real scoring chance, with Barnes seeing a couple of speculative drives charged down by the Palace backline.

And just over a minute after the restart, Murphy's superb whipped cross from the right was prodded home by Osula to give United the lead.

And just moments later, Joelinton's through ball found Joe Willock, who finished superbly across Palace stopper Walter Benítez - but his celebrations were curtailed by a VAR check, which determined the former Arsenal man was fractionally offside.

They didn't have to wait too long for a second, as with 57 minutes gone - and with the help of some adject defending from the Eagles - Nico González fed Dedić, whose assist for Barnes' well-taken fourth of the season was perfectly weighted.

Horníček did well to keep out an Adam Wharton's strike on what was a rare second half foray forward, and the Czech custodian had to be alert again 20 minutes from time to keep out substitute Darío Osorio's stinging drive from distance.

It capped a strong showing from Horníček while Jaissle will have been buoyed to have been able to give some minutes to fit-again duo Jacob Ramsey and Anthony Elanga, who both came off the bench in the closing stages of what was a pretty routine - and welcome - victory on the road for United, who move up to seventh in the Premier League table.

Newcastle United: Lukáš Horníček, Lewis Hall, Fabian Schär, Nico González, Joelinton (Sean Steur 85), Will Osula (Yoane Wissa 77), Harvey Barnes (Anthony Elanga 77), Jacob Murphy, Joe Willock (Jacob Ramsey 77), Dan Burn (c), Amar Dedić (Malick Thiaw 90)

Substitutes: Nick Pope, Sven Botman, Aladji Bamba, Bazoumana Touré