An important factor in the success of the amalgamation initiative was that three of the four co-ops involved – Dungarvan, Kilmeaden and Millvale – had been formed in the 1920s so that, by the 1950s, a new generation of younger and more progressive farmers had moved into leadership positions in these co-ops, and possessed the leadership qualities required to bring th initiative to fruition.  In other parts of the country, where there was a profusion of small co-ops, frequently with overlapping territories, the amalgamation process proved to be much more difficult to pursue and tended to produce very messy results.

Once the new Waterford Co-op was up and running, a further phase of external expansion and amalgamation was embarked upon in the 1970s, involving the absorption of Castelyons Co-op in east Cork, Glenmore and Ida in south Kilkenny, Shelburne Co-op in south Wexford and Southeast Farmers' Co-op in north Wexford/south Wicklow.  Further expansion into south Tipperary and Kilkenny, however, was stymied by the emergence of Avonmore Co-op in these areas in the 1970s.  As a result, Waterford Co-op now had acquired a crescent-shaped territory stretching from south Wicklow around the southeast corner of Ireland to east Cork.  For a period, Waterford was the leading co-op, in turnover terms, in the country, although it was in turn overtaken in time by the meteoric growth of both Avonmore and Kerry Co-op, established in 1974.

The formation and expansion of Waterford Co-op were accompanied by major restructuring of the dairy industry in the southeast region.  Milk processing was concentrated in just three locations: Kilmeaden, where a cheese factory was built in the 1966; Inch (on the Wicklow/Wexford border) where the production of Yoplait yoghurt commenced in 1974; and Dungarvan, which remained the main milk processing centre, with additional milk powder plants being added in 1964, 1968, 1973 and 1978, along with a casein plant in 1972.  EEC entry in 1973 provided a major stimulus to dairy farmers to expand milk production, and by the time milk quotas were introduced in 1984, Waterford Co-op was handling almost four times more milk than in 1970 (including those co-ops which subsequently joined Waterford).

Meanwhile, in 1963 Waterford Co-op introduced the bulk tank system for collecting milk directly from farms – the first co-op in the country to do so.  By 1980, almost all suppliers were using this system.  Milk separation therefore ceased at the branch creameries.  However, while some were closed, most remained open as stores and shops.  The daily trip to the local creamery which had become such an important part of the life of dairy farmers was now a thing of the past.