The hosts had won two and drawn one of their last three matches having opened the campaign with three straight defeats, but had no answers as Lazio put them to the sword on the back of a rampant first-half display.
A Hernanes free-kick and a brace by Miroslav Klose had the match won inside 35 minutes for the capital club, who remain well on the coat-tails of the league leaders after securing a fifth win from seven games.
Just five minutes were on the clock when Hernanes opened the scoring, the Brazilian curling his free-kick into the top-right corner of Mattia Perin's net.
The visitors doubled their lead in the 25 minute when Antonio Candreva picked out Klose, who calmly rounded Perin and passed into the empty goal.
Klose flashed another effort wide on the half-hour mark as Lazio continued to dominate, and within five minutes the Germany international had his second, heading home a Hernanes corner from the edge of the six-yard box.
Pescara finally carved out a decent chance on the stroke of the interval as Emmanuel Cascione powered a header on goal from Gianluca Caprari's cross but Federico Marchetti made a good save down low.
The second half was all about damage limitation for Pescara, with defender Antonio Balzano called into action to clear off the line from Stefano Mauri's deflected effort.
Hernanes drilled a shot over the bar and Perin saved well from Candreva as Lazio continued to pose a threat, while Pescara were twice denied a consolation with Marchetti saving first from Juan Quintero and then from Elvis Abbruscato.