The first of Kouzmanoff's four hits staked San Diego to a quick 3-0 lead with no outs in the top of the first.
Alonzo's only hit made it 6-0 with two outs in the third.
Will Venable had four hits with four runs and one RBI. Luis Rodriguez had two hits and two RBI, while Chase Headley drove in a run for the Padres, who broke a seven-game losing streak.
Winner Kevin Correia (6-7) surrendered three earned runs and eight hits in 5 2/3 innings before three relievers finished the contest.
John Bowker led San Francisco with two hits -- one a two-run, fifth-inning homer.
Fred Lewis and Edgar Renteria had one RBI apiece for the Giants, who fell seven games behind the National League West-leading Los Angeles Dodgers.
The losing pitcher was starter Barry Zito (5-9).
Copyright 2009 by United Press International.