Osborne was an active member of the Bay Street community, serving as a board member for Tim Hortons Inc. (TSX:THI) and a trustee of RioCan Real Estate Investment Trust (TSX:REI.UN) at the time of his death.
Postmedia spokeswoman Phyllise Gelfand said he died suddenly in Florida on Tuesday.
"It's a sad day for Postmedia and all the other corporate entities that he sat on," Postmedia president and CEO Paul Godfrey told The Canadian Press in an interview.
"He was by far the most outstanding director that I've ever served with."
The list of companies where Osborne held board positions is long and diverse, covering some of the country's most prominent media and telecom companies, as well as various energy firms.
Osborne was the president and chief executive of Maclean Hunter Ltd. in the mid-1980s when he first met Godfrey and worked as his boss. He held the top role at Maclean Hunter starting in 1986 until it was sold to Rogers Communications (TSX:RCI.B) in 1994.
"Ron was such a good director with respect to not only finance and corporate governance, but he had such high integrity," Godfrey said.
"Everybody wanted him to be on their board."
Osborne also served as president and chief executive of Ontario Power Generation Inc. and as a senior executive at BCE Inc. (TSX:BCE).
Later he was chairman at Four Seasons Holdings Inc. and Sun Life Financial Inc. (TSX:SLF).
Other companies where Osborne held board positions included Nortel Networks, Air Canada (TSX:AC.B), Torstar Corp. (TSX:TS.B) and Shell Canada.
He also held roles at the Shaw Festival and on the board of governors at Roy Thomson Hall in Toronto.
Note to readers: This is a corrected story. An earlier version gave an incorrect day for Osborne's death.