In the years 2011-2013 the studies were carried out, whose aim was to assess a yielding of oat-pea mixtures grown on seeds in organic farming. The field experiment was conducted at the Agricultural Advisory Center in Szepietowo. The cultivar of Pisum sativum (L.): Milva (semi-leafless cultivar) and Klif (with bipinnate leaves) was the first factor. The second factor concerned the percentage of P. sativum in mixture with Avena sativa (L.): 40, 60 and 80%. The study showed that the mixtures yield was significantly influenced by tested factors and the course of weather conditions. Increasing the percentage of legume seeds in the mixtures with semi-leafless cultivar Milwa as well as with cultivar of bipinnate leaves - Klif resulted in the decrease in their yields. In 2011 and 2013, higher yields were recorded for Milwa cultivar and, in more favorable moisture conditions, for Klif cultivar. Number of nodes with pods and the number of pods per plant in the both tested cultivars, regardless of the morphological composition, had not influence on a significant differentiation together with increasing the pea percentage in mixture with oat. Increasing of pea percentage in weight of sown seeds resulted in an increase in the number of seeds per plant in both pea cultivars only in the first year of the studies, while in the following years, it resulted in the reduction in the number of seeds. It was found that together with increase of pea percentage in mixture, the length of fruiting part and dry matter of siliques per plant were reduced. The composition of mixtures had a little effect on the height to the first pod and height of plants.