The 22-year-old has penned a three-year deal with the Dons following his departure from Bolton.
The Pittodrie side have also recruited teenage striker Lawrence Shankland from Queen's Park.
Manager Derek McInnes told the club's website: "Gregg is a player who will give us real pace and good balance, which is something I felt the team needed.
"He is a young player who has had a couple of frustrating years with injuries and not playing first-team football but he is a player with great ability and is someone who I am sure will be hugely beneficial to the team.
"I'm really looking forward to working with him and continuing his development."
- Sports & Recreation