The sowing date of winter oilseed rape affect plant development and yield to a large extent, but yield components have not been well documented yet in the conditions of Poland. Therefore, research was undertaken to determine the impact of the delayed date of winter oilseed rape on the development of plants and the quantity and quality of the seed yield. A field study was conducted in the seasons 2013/2014 -2015/2016 at the Experimental Institute of Cultivar Assessment in Skołoszów, Poland. Experimental factors were: the seed sowing date (optimal, delayed) and winter oilseed rape cultivars (Monolit, Arsenal F 1 ). This study has indicated that sowing the seeds in a delayed time affected shortening of the plant growing period, but it did not differentiate the seed yield. It has been found that the optimal sowing date increased the plant density prior to harvest, whereas a delayed sowing date resulted in an increase in the number of seeds per silique. The cultivar Arsenal F 1 increased seed yield by 0.87 t/ha as compared with the cultivar Monolit.Delayed sowing date increased the content of fibre and zinc in seeds, and decreased the content of protein, phosphorus and potassium as compared with the optimal time.