In organic farming, there are increasing problems with spring peas due to heavy pest infestation and late weed competition. Winter peas could be an interesting alternative. The expectations for winter peas are: a more effective weed control, higher N2 fixation because of the long growing season and a higher yield potential than spring varieties. The goal of a one-year field experiment was to examine the agronomic performance of pea stands intercropped with small populations of winter barley under production conditions of the Marchfeld cropping area. On two sowing dates three morphologically different winter pea varieties were mixed with winter barley. To further study the effects of competition, winter peas were grown in five densities. Winter peas and winter barley were also grown in pure stands. The experiment focused on the following questions: to what extent did the sowing date, variety, crop type and plant density influence on (i) the overwintering, (ii) the weed infestation and lodging resistance, and (iii) the dry matter and yield production? The early sowing date (sowing: 09/22/2010) survived the winter period only with substantial losses. EFB33 showed the lowest overwintering. Winter peas sown late (sowing: 14/10/2010) survived up to 90%. Different densities had no effects on the overwintering and the weed infestation. Intercrops with winter barley could not suppress weeds better than winter peas in pure stands. The abundant leaf mass of regular-leaf genotypes did not impact weed growth compared with semi-leafless genotypes. Similarly, there was no difference in yield formation between winter peas in pure and mixed stands. The semi-leafless variety Cherokee had the highest grain yield with 1.676 kg/ha. The regular-leaf variety Griechische also achieved a higher yield (1.352 kg/ha) than the EFB33 (775 kg/ha). High weed infestation, complete lodging combined with uneven ripening, especially in the variety EFB33, led to significant yield losses. In conclusion, winter pea is not yet a satisfactory replacement for spring peas.