The aim of the study was to determine the yield per ha, chemical composition, in vitro true digestibility (IVTD), and nutritive value of faba bean seeds and naked oat grain grown in pure sowing or in mixtures (effect of cultivation method) under organic farming conditions. The experiment was carried out on two faba bean cultivars (Olga, a low tannin, traditional variety, and Optimal, a high tannin variety with terminal inflorescences), and naked oat (cv. Polar). The proportions of faba been to oat in sowing mixtures, in relation to optimum sowing density for each species grown in a pure stand (taken as 100%), were 0:100, 25:75, 50:50, 75:25, and 100:0, respectively. The highest grain yield (3.12 t/ha) and yield of crude protein (978 kg/ha) per ha were obtained from the mixture of 75% faba bean (Optimal) and 25% oat. Increasing the proportion of oat in the mixtures decreased their crude protein content with little impact on other nutrient contents, in vitro true digestibility, UFL and PDI values. In faba bean, greater differences among analysed parameters were observed between cultivars than between cultivation methods.