The burger chain was snapped up by Famous Brands, which also owns Wimpy, last month for £120m and boss Alasdair Murdoch has got the green light to open up to 15 new restaurants a year.
"We're opening 12 restaurants this year and will open 12 to 15 per year over the next five years, that's not too aggressive," he told the Press Association.
The move would see GBK, which currently employs 2,000, take on 2,500 more staff and see its store tally double to 150.
Murdoch also said he wants to double turnover, which hit £65 million last year, by 2021.
Industry estimates put the value of the UK burger market at £2.8 billion, and a number of US chains such as Five Guys and Shake Shack have piled into the so-called "premium" segment of the market recently.
But the GBK chief said he relished the challenge competition brings and does not believe that the UK market has reached saturation.
"Competition is good for us. It's possible that growth might slow, but everyone loves a good burger so I'm not worried."
He also said the firm will "fight" for access to a big labour market in light of Government pronouncements stipulating that Britain is on course to crash out of the single market and pursue a "hard Brexit".
"Our workforce is very important for us, and we will fight hard for access to a big labour market," Murdoch added.
At the time of the takeover, Famous Brands said that fears of a Brexit effect on the eating out market "appear negligible", adding that it would look to export the GBK brand to South Africa.