Mark Streit was a key member of the Montreal power play that dominated the league last season. ((Dale MacMillan/Getty Images))

Mark Streit is leaving Montreal for Long Island.

The power-play specialist, who can play both defence and forward, signed a $20.5-million, four-year deal with the New York Islanders on Tuesday.

Streit spent the last three seasons with the Montreal Canadiens and helped them develop one of the NHL's best power plays.

In 205 NHL games with Montreal, he has 25 goals and 109 points.

The 30-year-old is a former Swiss Olympian.