The visitors recorded their first win at Estadi Cornella-El Prat.
Neither team dominated the proceedings early in the game as Espanyol were succeeding in their efforts to break the visitors' slick passing game. Still, Barcelona got the first real chance of the game in the 10th minute when Lionel Messi missed the target with on open goal.
Just before the twenty-minute mark the Blaugrana took the lead through Pedro. With Jose Maria Callejon struggling on the ground in Barca's half of the pitch, the visitors attacked on the break and the young Spain international put the finishing touch after being fed by Messi.
Espanyol tried to come back into the game quickly and almost drew the leveled in the 22nd minute when Luis Garcia saw a wonderful free-kick saved by Victor Valdes. Once again, however, Barcelona hit the hosts on the break with half an hour on the clock as Xavi volleyed skilfully past Carlos Kameni on his second attempt to give the Blaugrana a two-goal cushion.
Espanyol had not given up just yet and went close in the 35th minute when Callejon was released in the box by Luis Garcia, but saw his powerful finish stopped by Valdes. In the last seconds of the first half David Villa was denied by a brilliant tackle from Victor Ruiz.
Five minutes into the second half and Barcelona could have made it three, had it not been for Pedro's poor decision to pass instead of finish himself. The Blaugrana continued to dominate the game in the following minutes and deservedly scored a third in the 60th minute and it was Pedro who completed his brace as he forced a rebound into the net from a yard out.
Espanyol's answer was lightning fast as they scored one of their own just three minutes later. Callejon put in a wonderful through ball to Osvaldo, who raced easily past Carles Puyol and clinically finished past Valdes from the right side of the box.
The goal gave the hosts much needed impetus and they started playing with a very high defensive line and soon paid for that. In the 74th minute Gerard Pique was released on the right by Sergio Busquets, but blasted his shot over the bar with only the goalkeeper to beat.
Villa made no such mistake two minutes later as he precisely finished past Kameni after being released by Messi with a through ball. Eight minutes later, in a carbon copy of this situation, Villa bagged his brace to put the icing on the cake.
Following tonight's result Barcelona cement first place in the standings with 43 points, while Espanyol are fourth with 28 but could tumble down after the rest of the weekend games. Mauricio Pochettino's team's next league game is a visit to Valencia on January 2, while The Blaugrana host Levante on the same day.