"Peter is an experienced player and has helped his former club to the Second Division Championship, as well as being part of the Watford side that got promotion," manager Barry Fry told the clubs official website.
"He has also represented Northern Ireland on many occasions and is a very talented left-sided player. He will give us the necessary balance to the team and is a great addition to the squad.
"Craig has agreed a two year deal following his release from Barnsley. He played 50 times for the Tykes last term and has played over 120 games in the last three seasons in this division and we are delighted to have signed him.
"Both players have trained with the club during the last month, they have fitted in well and get on well with all the players. We wish them both a very successful time at the club and they will certainly be good acquisitions for this Football Club."