This paper deals with lagged effects of winter catch crops on the growth, yield, and quality of onion. Each autumn for two consecutive years (2009 and 2010), hairy vetch (VV), white clover (TR), winter rye (SC), Italian ryegrass (LM), and winter turnip rape (BRT) were sown as winter catch crops. In the next two springs (2010 and 2011) they were ploughed into the soil, and after them sweet corn was grown. Similarly, in the spring of 2010 and 2011, the farmyard manure (FYM) was applied at a dose of 30 t·ha-1 to plots with no incorporated crops, and afterwards sweet corn was planted. Finally, sweet corn was followed by the ‘Sochaczewska’ and ‘Stuttgarter Riesen’ varieties of onion, grown in 2011 and in 2012. The effect of catch crops on onion was compared with the effect of the farmyard manure and with control plants (without organic fertilizer). The highest onion yield was recorded on the plots with incorporated FYM and hairy vetch catch crop (VV). Moreover, a statistically similar marketable yield was also recorded on the plots with the incorporated catch crops of SC, LM, BRT, and TR. Incorporated catch crops affected nutrient content in onion. The most dry matter was obtained in the onion grown on plots with incorporated LM and FYM and on control. The onion grown the second year after the incorporation of SC, BRT, VV catch crops and farmyard manure was richer in protein than that grown on control. The content of sugars was the highest in the onion grown after BRT and the lowest after VV. Further research on the effectiveness of the catch crops used as green manure to grow vegetables is needed, in order to choose the best one in the following sequence: winter catch crops – sweet corn – onion.