It wants to find up to 10 sites across the province, three in Greater Belfast, and the others in larger towns. But it would not confirm if Simply Food would be introduced in Wales and Scotland in the new expansion drive.
All sites shortlisted so far are in greater London and the south east, with one scheduled to open at Brighton station in November.
M&S will stick to the standard Simply Food offer of ready meals, convenience foods, instore bakery, wines and newspapers as it rolls out Simply Food.
The ideal size for a store has been set at between 2,500 sq ft and 3,500 sq ft depending on site availability.
But a spokesman said location, not extended opening hours, was the primary driver.
Bryan Gray, chief executive of the Northern Irieland Independent Retail Trade Association, said: "We are confident our members will be able to resist this new competition."