Irish dairy production is primarily produced from a spring calving grazing system with the use of concentrate supplementation in the spring and autumn. Problems with milk quality are more pronounced in such a seasonal system where the majority of the herd enter into late lactation at the same time. Supplementation may offer a means of improving milk quality and composition. Oat supplementation has shown improvements in milk yield and composition in early lactation, while supplementation with vitamin E (VE) may improve cell structure and milk quality. Therefore, the objective of this research was to investigate the effect of concentrate type and VE on milk quality and processability parameters in late lactation grazing dairy cows. Forty 8 Holsten Friesian dairy cows were blocked on days in milk (+185DIM) and balanced for parity, pre-experimental milk yield and milk composition, predicted 305day milk yield and BCS. Cows were randomly assigned to 1 of 4 dietary treatments in a randomized complete block design (n = 12). The dietary treatments (T) were grass only (T1); grass + 2.6kg DM barley based concentrate +350IU VE/kg (T2): grass + 2.6kg DM oat based concentrate +350IU VE/kg (T3) and grass + 2.6kg DM oat + 1050IU VE/kg based concentrate (T4). The diets were fed for a 14day acclimatization period and then for a further 49days. Milk samples from each treatment were pooled into 3 subsamples (n = 3). Cows offered T3 had a lower milk pH (6.60) than T1 (6.62, P = 0.02). Rennet coagulation time was reduced in milk from cows offered T4 (2.49 min, P = 0.004), and increased in milk from cows offered T2 (5.36 min, P = 0.007) compared with cows offered T1 (4.16 min). Cows offered T3 and T4 had increased ethanol stability (67.29%, P = 0.003; and 67.33% P = 0.002 respectively) in comparison to T1 (65.54%). In conclusion, concentrate supplementation with oats or high VE had a positive effect on milk quality and processability. Supplementing dairy cows with oats improved milk pH. Offering a high level of VE to dairy cows reduced rennet coagulation time and increased ethanol stability of milk.