Groat per cent and milling yield are important quality traits of oat (Avena sativa L.); however, accurate testing for these traits using existing methods can be time-consuming and labour-intensive. In this study digital imaging analysis (DIA) was used to estimate the mass of mechanically dehulled oat constituents (hulls, undamaged and broken groats), replacing hand sorting and weighing of these constituents in a test method measuring groat per cent and milling yield. Groat per cent values estimated using DIA had a standard error of prediction (SEP) of 0·57 and a correlation coefficient of 0·995 compared to the manual method. Milling yield values estimated using DIA had a SEP of 0·98 and a correlation coefficient of 0·993 compared to the manual method. Incorporating DIA into the test method allowed considerable savings of time and labour in performing these tests.