Heather Humphreys, Irish Minister for Arts, Heritage and the Gaeltacht, and Arlene Foster, Northern Irish Minister for Enterprise, Trade and Investment, were on hand yesterday to officially open the €7.8m facility at GII's existing County Cavan site.
As a result of the investment, milk protein powder production at the site will more than double, from 4,000 tonnes to 10,000 tonnes.
The Virginia plant extension is the latest product of GII's €200m (US$250m) investment plan.
"GII has a strong investment programme of over €200m which is designed to position the business for future growth. While we are conscious of current fluctuation in commodity pricing, the long range outlook for the business and for suppliers is positive - with a growing demand from customers for the high quality milk protein we will be producing here in Virginia," said Jim Bergin, CEO, GII.
GII is a joint venture between Glanbia and its largest shareholder, Glanbia Cooperative Society, which hold 40% and 60% stakes respectively.
It currently operates two facilities - the aforementioned County Cavan site and another in Ballyragget, Kilkenny.
The joint venture was established in 2012 in advance of the April 2015 European Union (EU) milk quota abolition.
Under the quota system, which was introduced in 1984 to address overproduction, each EU Member State has two production limits - one for deliveries to processors and the other for direct sales at farm level.
If exceeded by an individual Member State, a fine called a superlevy is issued.
During the 2013/14 season, Irish producers delivered over 5.8m tonnes of raw milk to processors
As a result of the quota abolition, milk production in Ireland is forecast to increase by around 50% by 2020.
"The opening of our new plant ensures that both GII and our farmer suppliers will be able to capitalise on the generational opportunity that is provided by the ending of the milk quota next year," said Bergin.