Öbster began his youth career with SK Bischofshofen and in 2001 joined BNZ Salzburg. After impressing with BNZ, Öbster was called up by the SV Austria Salzburg first team and debuted in the Austrian Bundesliga as a 17 year old. After receiving limited playing time with Salzburg, Öbster was loaned to LASK Linz in 2003, during his time with Linz he was a regular starter as a left-sided midfielder appearing in 28 matches and notching 2 goals. After an impressive season with Linz, Öbster returned to SV Austria Salzburg and was a key reserve for the club. In 2005, SV Austria Salzburg was acquired by Red Bull and Öbster remained with the first team appearing in 7 league matches. Over the next few years he would alternate between the first team and Red Bull Juniors playing in the Austrian Football First League, in which he appeared in 30 matches scoring 9 goals. In the 2008-09 season Öbster appeared in 5 league matches and 4 UEFA Cup qualification matches in which he scored 2 goals. He also appeared in 3 Austrian Cup matches scoring 1 goal.