Beardsley will replace Alan Thompson, who left for Celtic this summer.
Beardsley: "This is a fantastic opportunity for me and one that I am thrilled to have been given. I can't wait to get cracking with what I know are a very talented set of players."
Steve Stone will assist Beardsley with the reserves.
Chris Hughton: "This is an excellent opportunity for Peter and Steve. I hope their services will be of great benefit to the club."