BACKGROUND: Mixtures of cereal cultivars grown together generally enhance yield and reduce disease but end-users will not accept them for quality uses. Whilst mixtures of cultivars with very different quality may be problematic, other combinations may be complementary. The common origin of Maris Otter for quality in winter barley may enable the benefits of complex mixtures to be exploited without quality compromises. RESULTS: Seven winter barley cultivar monocultures and all their equal proportion mixtures from two to seven components were grown in a replicated field trial and assessed for yield, thousand grain weight, disease and six malting quality parameters. Data was analysed by ANOVA, REML and principal component analyses to determine the contribution of particular varieties or combinations of varieties to crop performance. Yield was positively correlated with component number. Three cultivars contributed strongly to different trait data, but sometimes in opposite directions. Pipkin had small grain and therefore contributed negatively to thousand grain weight, but positively to several quality traits, whereas Gleam contributed negatively to the same quality traits but strongly positively to yield. Compromise choices such as Melanie could be identified in this way, combining strong yield and thousand grain weight characteristics with neutral quality traits. Interactions in mixtures with Maris Otter, from which most of the cultivars are likely to derive some of their quality traits, were generally less apparent for quality than for yield. CONCLUSIONS: Complex mixtures gave yield benefits generally without compromising quality, and analysis methods were developed to identify the beneficial or negative effects of component cultivars on malting quality traits, thereby providing data for optimising mixtures design.