Having had a succesful loan period at Barnet, manager Paul Fairclough has been quick in the transfer market to make the deal a permanent one.
Speaking to the official Barnet website, Birchall said "I have really enjoyed my loan spell and hopefully I can keep learning and keep improving.
"I had a long spell out at Mansfield where I didn't play for a long time. During my loan spell at Barnet I really enjoyed the club atmosphere, the fans support and, of course, scoring goals."