O'Rourke said he was proud of the Laing name. He said: "The Laing brand is known around the world and respected throughout the industry and it is one we intend to build on."
The group announced a new Laing O'Rourke board, which includes former Alfred McAlpine main board director Andy White and former Sir Robert McAlpine director Gus Roche, who will be group procurement director.
The board also includes the former managing director of Laing Construction Brian Richardson who has a non-executive directorship.
Alfred McAlpine announced last month the shock departure of White, who ran the group's successful capital projects division.
White will be chief operating officer of Laing Construction. His counterpart at O'Rourke will be Steve Hollingshead.
The group also announced a return to Laing for Anna Stewart, who has been appointed commercial director of Laing Construction.