Miguel Montero, Gerardo Parra and Justin Upton knocked in one run each to stake Garland and the Diamondbacks to a 3-0 lead.
Montero ended with two hits and two RBI. Upton had four hits, while Parra drove in two for the Diamondbacks, who have won seven of eight.
Garland (5-8) walked one batter and struck out five.
Florida's run scored on Jorge Cantu's third-inning single. He had three of the eight hits for the Marlins, who have lost four of six.
Losing pitcher Sean West (3-4) surrendered five earned runs and nine hits in 4 2/3 innings.
Copyright 2009 by United Press International.