The bakery chain is riding the wave of the movement, which encourages people to go meat and dairy-free for the whole of January, with its vegan steak bake, made with meat substitute Quorn.
As of Thursday, Greggs’ new offering is available in 1,300 of its shops across the UK and will expand to all 2,000 locations on 16 January.
People were reportedly queuing outside a Newcastle branch on Wednesday night, when it made a late-night premiere.
Greggs has been a delight for investors, with its shares in demand after sales rose 12.4% in the six weeks to 9 November.
Management also said in its November update, that full-year pre-tax profit would be higher than expected, with analysts at Peel Hunt bumping up their forecast from £110mln to £115mln while anticipating further increases.
Greggs shares rose 3% to 2,367.05p after lunch on Thursday.