The engineer - who was one of the main players in the drama that unfolded at Holyrood - walked away from the practice in late 2004 not long before it completed the hugely controversial scheme.
RMJM worked in partnership with Enric Miralles' practice EMBT on the design of Holyrood, a relationship that became increasingly fraught as things began to go wrong.
It was widely rumoured at the time that the stress of the delays, cost rises and constant media scrutiny became too much for Stewart.
But now Scottish property developer Hazledene has appointed him an executive director.
Stewart will help deliver the strategic direction of the group, and be involved with the operations of the company's two main trading divisions, Hazledene Estates and Hazledene Homes.
'This is a very exciting opportunity for me,' Stewart said.
Throughout my career I have worked with a number of different developers, but I have been particularly impressed by Hazledene's dynamic and quality approach to its projects.'