The latest supermarket share figures show a strong performance from Dunnes - growing sales by 6.3% in the past 12 weeks to reach a market share of 22.2%. That is up from 21% in the same period last year.
However Tesco still retains the top spot. The Kantar Worldpanel stastisitics show that only Lidl outperformed, with market growth in sales of 6.4%.
Insight manager at Kantar, Cliona Lynch, explains: "Dunnes continued focus on its 'Shop & Save' voucher scheme is encouraging consumers to buy a bigger basket on each shop."
"The average Dunnes visitor is buying 18 items per trip compared with a market average of 13 - an increase of three items per basket on this time last year and an additional €5 through the tills on each shop," she added.
Tesco has retained its position as Ireland's number one retailer with a 25.1% share of the market, despite a sales decline of 3.3%.
SuperValu sales grew just behind the market at 0.6% and share remained flat at 24.7%.
In contrast to Ireland's three largest retailers, Aldi and Lidl have continued to recruit shoppers to their stores. But the growth in shopper numbers at discounters is slowing.
Aldi gained 28,000 new shoppers in the past 12 weeks compared with 80,000 this time last year - while Lidl picked up 6,000, down from 53,000 in the 12 weeks to June 2014.
Aldi has also seen growth in basket size slow, an area in which Lidl is outperforming.