Gala, the mainly rural-based convenience chain, plans a €40m investment next year that will add 30 outlets to its current 220.
Barry's of Mallow, a distribution company that owns the Costcutter franchise, is to take its total to more than 150 with 40 new stores.
Retail sales at Gala, a franchise group set up by independent wholesalers in 1998, have grown 26% to €507m in the current year.
Speaking at the Gala annual conference in Athlone, chief executive Tom Keogh said the group's success had been built on its rural growth. "We've consistently opened shops in areas where other retail groups haven't gone."
There was no sign of saturation in the Irish convenience sector, he said, though a slowdown in openings could come in three years when the growth in house-building eases off.
In addition to 112 Costcutters, Barry's has 91 Quik Pick stores. Turnover is set to reach €570m this year and €680m in 2007 with the addition of new outlets.
Next year Barry's is planning to rename itself Barry's Group and also launch new corporate and retail brands.