Transport Scotland has published the OJEU notice for the works which are expected to start early next year.
Transport Minister Keith Brown said: “It is vital work continues in pressing ahead with the Maybole bypass.
“The A77 is one of the key routes to the newly opened Loch Ryan ports and as a Government we are determined to enhance connections to and from this major transport hub.
“This latest milestone to allow ground investigations works to commence and gather valuable information to inform further detailed design and assessment and confirm the preferred route for the bypass.”
Draft road orders outlining the scheme design proposals are expected to be published in Autumn 2013.