The 22-year-old has moved to League One promotion hopefuls Swindon Town for an undisclosed fee on an 18-month contract.
Barker made just two substitute appearances for County, at Cheltenham Town and Oxford United, having arrived on loan from the Amex Stadium in November.
On arrival Barker told the Argus he was hopeful of making a big impact at Rodney Parade.
“It’s nice to get some game time and it's a great move for me,” he said in November.
“Now with Christmas and lots of games, I want to help the team as much as I can.
“It’s a great chance for me, all a player wants is a chance to show what they can do and I want to do as well as I can.”
Exiles boss Justin Edinburgh was also optimistic that Barker could contribute, adding: “He’s impressed us in the Brighton development games, he’s been around their first team squad and we hope he enjoys his time here, we’re delighted to have him.”
But Barker played just six minutes at Cheltenham and 23 minutes at Oxford. Both matches ended 0-0.
He has also made four substitute appearances for Albion, including one this season.
“George has worked hard and made good progress with the club, but his opportunities here are limited,” Albion’s head of football operations David Burke told the club website.
Barker, who signed his first professional contract with Brighton in 2010 after coming through Albion’s centre of excellence, also had a loan spell at Barnet in League Two last season before making his first-team debut for the Seagulls in the Championship at Barnsley.
“On behalf of the Albion, I'd like to thank him for his time at the club and wish him well with Swindon and in his future career,” added Burke.
Barker got his Swindon career off to a good start by scoring in Town’s 3-2 defeat to Birmingham City in a development XI fixture on Tuesday.
The striker will go straight into manager Mark Cooper’s match day squad for the visit of Peterborough United in League One on Saturday.