The result comes just four weeks ahead of the World Championships.
Placed third after his first run and 0.44seconds behind the leader, Peters put together a tactically smart second run. Making good use of the fall line to generate speed onto the flat section of the course Peters shot into second place ahead of Sochi gold medallist Christoph Kunz (SUI).
German Georg Kreiter took the win with two fastest runs and a combined time of 1:52.06 with Peters just behind in 1:52.64 and Kunz third in 1:52.71.
Races continue in St. Moritz on Tuesday (3 February) with another edition of giant slalom, before continuing on Wednesday (4 February) and Thursday (5 February) with slalom races.