He played junior hockey for the Smiths Falls Bears of the Central Junior Hockey League from 1963 to 1967. In 1966-67, Tosh was named the league's outstanding defenceman. He was picked up by the Cornwall Royals for the 1966-67 Eastern Canada Memorial Cup Playoffs, where he broke his right hand in a fight with Marc Tardif.
The New York Rangers chose him 15th overall in the 1967 NHL Amateur Draft and then traded him to the Pittsburgh Penguins. Tosh suffered an ankle injury in the 1967 pre-season and was assigned to the Fort Wayne Komets. Tosh retired in 1968 after attending the Penguins' training camp.