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.”
On the capture of 17-year-old Shankland - who has signed a two-year deal - McInnes added: “I’m delighted to have secured Lawrence.
“He scored a lot of goals for Queen’s Park last season and we feel he is an excellent acquisition for the club.
“He will now gain the benefit of training full time and will play regularly at under-20 level with a view to forcing his way in to the first team.
“Lawrence is definitely one for the future with the potential we see in him.
“He has shown a great deal of maturity to score as many goals as he did last season in the Third Division and by working closely with Neil Cooper, myself and Tony [Docherty] he will only continue to improve.”