 Tosio began his professional career playing for EHC Chur, after playing in junior teams of the club since he was 8 years old.He stayed with Chur until the end of the 1986/87 season, twice winning the NLB championship and thus promoting to the NLA (in 1984 and 1986).He then played 14 years for SC Bern, the first game on 3 October 1987 against EHC Biel and the final one on 20 March 2001 against HC Lugano.