The bar group, which is owned by Stonegate Pub Company, first introduced real ale to selected bars across its estate eighteen months ago.
Real ale is now available in 60 of Slug and Lettuce’s 75 bars, with 25 bars selling over the national average in real ale sales per week.
Twenty bars, which are currently cask marque accredited, will host the festival, offering a choice of ten ales from national to local brewers.
Among the real ales available will be Marston’s Pedigree and Young’s Bombardier along with local championship winning ales such as Triple FFF’s Alton’s Pride and Salopian’s, Shropshire Gold.
Alan Armstrong, sales and marketing coordinator for Slug and Lettuce, said: “The customer response we received when we first introduced real ale into our bars was hugely positive.
“Real ale consumption has since gone from strength to strength across the estate so we are delighted to launch the first ever Slug and Lettuce Real Ale Festival, the first of many.”