Edmonton trailed 2-0 after the first period, but scored the next four goals to come away with the victory.
After the Oilers' Ales Hemsky scored in the second period, Ladislav Smid got the equalizer with less than 5 minutes left in the frame.
Petry then put Edmonton ahead 8 minutes into third and Ryan Jones quickly added an insurance tally as the Oilers wrapped up a six-game road trip with a pair of wins.
Devan Dubnyk stopped 29 shots in the triumph.
Carey Price was tagged with the loss, allowing four goals on 32 shots.