The group announced it had reached 2,507 Premier stores at the end of March, confirming it as the second biggest symbol group by store numbers and rapidly closing on Spar's number one spot.
Since it was relaunched 12 months ago, the group has attracted more than 400 new stores a net gain of around 270 including 170 smaller outlets under the Express banner.
The celebration kicked off on Wednesday this week and runs until May 11. Every consumer who spends £5 or more in a Premier store (including tobacco but not top-ups) will receive a scratchcard, with one in three cards guaranteed a prize ranging from a free product up to six top prizes of £2,500 in cash.
Booker is investing £250,000 in marketing support for the promotion, including regional press advertising and more than three million consumer leaflets.
Retail sales director Steve Fox commented: "Our aim is for Premier to be the biggest and best symbol group, providing the benefits of scale while being able to think local."