Despite sales picking up in September after a "challenging" summer, the company said it is in talks with staff over cutting employee hours “to minimise the risk of job losses” when the furlough scheme ends in October.
The Newcastle-based business said the "outlook for trading remains uncertain" as Covid infections rise again, bringing the treat of further restrictions.
The firm said it has completed a review of its trading operations as it sought to reflect the "estimated level of demand from November onwards”.
It told investors its “immediate priority” is to complete the consultation and confirm the financial impact of the move when the consultation ends in November.
The food-to-go specialist said it suffered a “difficult" August, as the closure of seated areas meant it was unable to benefit from Eat Out to Help Out.
High temperatures also kept customers away, it said.
Sales have picked up as the company continues its coronavirus recovery with more people eating meals outside of their homes in September, which it believes helped to drive improvements, but sales remain 25% down on last year.
Since reopening on July 2, its like-for-like sales averaged at 71.2% of its levels from 2019 for the 12-week period to September 26.
In the past month, covering the four weeks to September 26, like-for-like sales were at 76.1% of its levels from the same period last year, as trading improved.
Greggs said its digital business is “developing quickly” after increased investment during the lockdown period, partnering with food delivery operator Just Eat.
In a statement, Greggs said: “The outlook for trading remains uncertain, with rising Covid-19 infection rates leading to increasing risks of supply chain interruption and further restrictions on customer activities out of the home.
“In these challenging conditions our teams continue to work hard and have proven our ability to operate with social distancing and adapt to new digital channels.”