Digestion trials were carried out using 16 mature ewes fed diets based on grass or lucerne hay supplemented with 25 or 40% of either whole or crushed barley grain. The amount of whole grain voided in faeces was also evaluated. The study was conducted in two repeated Latin squares design separately for each type of hay, with treatments being two physical forms of grain and two concentrate-to-forage ratios. Except for a slight decrease in dry matter and N digestibility in lucerne hay based diets, the physical form of grain did not affect DM and ADF digestibility or N balance, irrespective of the concentrate-to-forage ratio (P > 0.05). The amount of whole grain voided in faeces was 4.7-10.2%, however considerable variation among ewes was observed. An increase in the level of grain in the diet from 25 to 40% increased DM digestibility (P < 0.01), whilst the grain level had no effect on ADF digestibility. N balance was improved by increasing the level of grain only when grass hay diets were fed. The results of this study show that, at levels up to 40% in the diet, whole barley grain can be effectively utilized by mature ewes fed hay based diets.