Eusebio Sacristan's men headed to the Estadi Cornella-El Prat without a victory in their last six away La Liga encounters - a run that dated back to late October when David Moyes was still at the helm.
However, from the moment that Jonathas pounced on a defensive error in the fifth minute to break the deadlock, the visitors were in complete control.
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Eighteen-year-old Mikel Oyarzabal's first senior goal for the Basque Country-based outfit in the 52nd minute made it 3-0 - a goal that was met by a barrage of jeers from the home faithful.
The hostile atmosphere then intensified further when Diego Reyes added a fourth goal with his head in the 55th minute to end any slim chance of a comeback for the hosts.
As the match ticked towards stoppage time Sociedad nabbed a fifth goal as Brazilian centre-forward Jonathas fired inside the right-hand post from close range.
The win has lifted Sociedad up to 11th position, five points ahead of Espanyol in 17th.