Grass utilisation is a key factor contributing to the profitability of grassland farms. This study examined the grazing utilisation of the 30 perennial ryegrass (Lolium perenne L.) varieties on the Irish Recommended List 2016. Plots were grazed by dairy cows from March to November 2017 on 11 occasions. Pre-grazing yield and height, post-grazing height and herbage removal were quantified. Varieties differed in grazing utilisation (P < 0.001), with post-grazing heights ranging from 3.7 to 4.8 cm. ‘Residual grazed height’ (RGH) was derived to measure grazing utilisation as the difference between predicted post-grazing height and actual post-grazing height. Most tetraploids outperformed diploids for grazing utilisation and despite desirable RGH values being negatively associated with grazing yield, varietal diversity indicated a potential for improvement. Further research is needed to determine the consistency of these differences and to determine how to assign an economic value to this grazing efficiency trait.