Fungal isolations and fungicide efficacy trials were carried out to determine the possible causes of discoloration in oat groats and potential control measures. Alternaria species and Microdochium nivale were isolated from field samples, and Fusarium poae was found in glasshouse tests. Symptoms could be induced reliably in the field through the use of a mist irrigation system. The cultivar ‘Gerald’ was most resistant followed by ‘Jalna’. Cultivar ‘Image’ was most severely affected by discoloration and ‘Millennium’ was of intermediate susceptibility. None of the 28 fungicide-timing combinations used in the field trials affected the occurrence of discoloured groats. It was concluded that the best strategy for minimizing risk of discoloured groats would be screening new cultivars or breeding material in mist-irrigated field trials for genetically based resistance.