The cabinet secretary for rural affairs and the environment, Richard Lochhead, confirmed the appointments yesterday ahead of his speech at today's Agriscot event at Ingliston.
McLaren is to take over from Donald Biggar as the chairman of QMS next April.
McLaren, who has led the NFU Scotland for the past four years, steps down at the Union annual meeting next February.
His appointment as QMS chair will make him the second Union president to move from their headquarters at the Rural Centre at Ingliston downstairs to the QMS headquarters in the same complex following a similar move by Jim Walker.
Lochhead also named five new members of the QMS board - including Grand Slam winning former Scotland rugby skipper David Sole.
Other new board members, who will also join in April, are John Scott, Johnny Mackey and John Craig. Alan McNaughton will join the board immediately to fill the position left by Danny Miller, who resigned in February this year.
Lochhead said: "I am delighted to appoint Jim as the new chair and bring Alan, John, Johnny, David and John on to the board of Quality Meat Scotland. They will bring a wealth of expertise, experience and passion to the organisation.
"Quality Meat Scotland has an excellent track record of delivering real benefits for the Scottish red meat supply chain and it has been ably led by Donald and his board. I'd like to take this opportunity to thank them for all for their hard work.
"Jim's leadership at NFUS has been hugely positive for Scottish farming.
"I'm absolutely delighted that as that chapter comes to a close, the sector will continue to benefit from his talent and energy.
"In the past, there has been criticism that there are no women on the board and I'm disappointed that this is the case again. I know there are many women involved in the livestock industry who could make a valuable contribution and as a result, there will be a further round of appointments next year."
Outgoing chair, Biggar said: "I'm delighted that so many skilled applicants were interested in taking up these positions and I welcome the cabinet secretary's selection of very well-qualified and able individuals.
"I'm sure I echo the sentiments of the other board members who are standing down in April when I say that the organisation is in great shape and I'm sure it will continue to contribute to a sustainable and prosperous red meat industry in Scotland.
"Quality Meat Scotland carries out a huge and diverse workload and the new board has a lot to look forward to being at the helm of a dynamic and hard-working organisation.We wish Jim and the new board every success."
McNaughton is a director of McIntosh Donald, part of the Vion Food Scotland group, and senior vice-president of the Scottish Association of Meat Wholesalers. Scott is a farmer in Tain while Craig is operations director with transport group AK Stoddart, Broxburn, and Mackey is a farmer in Blairgowrie in Perthshire.