Under the research project conducted in the years 2007 – 2008, the productivity of oats and its mixture with barley were investigated in three districts (gminas): Sanok, Zarszyn, and Besko. The evaluation performed comprised the components of yield structure and those selected morphological traits of the plants, which were related with the crop yield of the plants. Each year, the samples being characteristic for pure sowing and mixed stands were taken from 30 experimental fields included in the project. The grain yields of oats grown using pure sowing and mixed stands did not differ statistically significantly. The generative shoot density of mixed plants was higher if compared with the pure sowing and depended on the location of fields. The oats grown using mixed stands was characterized by a more advantageous crop yield index owing to shorter straw. The panicle length did not depend on the cultivation method. The number of seeds per oat panicle and the weight of 1000 grains were determined by the group effect of the methods of sowing applied and the vegetation periods. A higher number of grains in one panicle of oats grown in mixed stands was reported in 2008 and caused the weight of 1000 grains to drop. The sowing method did not significantly impact the weight of a single culm, panicle, and rachis. The morphological traits of the plants were strongly impacted by the vegetation seasons; consequently, this confirms the known sensitivity of oats to the course of weather conditions.