Real Sociedad moved up to ninth in the Primera Division table after they demolished Rayo Vallecano at the Anoeta.
Carlos Vela scored twice in the first half, while Martinez Mikel Gonzalez and Gonzalo Castro completed the rout in the second period.
Vallecano headed into the match into good form after consecutive victories over Malaga and Celta Vigo had lifted them up to 10th in the table, however they never got going and rarely troubled Claudio Bravo in the home goal.
Sociedad whose surprise victory at Malaga last weekend was their first in six matches took the lead just after the half hour mark through Vela, who powered home from the edge of the six yard box after he was played in by Diego Ifran.
It was the first real effort on goal and the second led to an equally positive outcome for the home side.
Once again it was Vela as he shot low from the right-hand side of the box, just two minutes after he opened the scoring.
The hosts were rampant and after 35 minutes Vallecano stopper David Cobeno made his first save of the evening, tipping over Ruben Pardo's 20-yard effort.
He was called into action again less than a minute later, this time parrying Diez Carlos Martinez's header away from danger.
Jose Manuel Casado replaced Andrija Delibasic at the break for Vallecano and the change seemed to work as they saw more of the ball although efforts from Roberto Trashorras, Alejandro Dominguez and Medina Piti all missed the target.
It took the home side to show them how to do it and on the hour mark they were three ahead as Gonzalez converted from close range.
Three became four 14 minutes from time Castro got on the end of a Pardo pass from 12 yards out to fire past Cobeno.
David Zurutuza hit the post for Sociedad with four minutes left, but Philippe Montanier will be delighted after watching his side pick up their biggest win of the campaign to date.