Compact and healthy seedlings of Brassica increase the crop production and improve vegetable quality. Different climatic conditions and extensive light can cause young plants to become elongated and spindly. We investigated the effects of end-of-day (EOD) treatment on plant height (cm) of the seedlings of three cultivars of each of the following species: cauliflower (‘Delfino’, ‘Freedom’ and ‘Momentum’), broccoli (‘Achilles’, ‘Ironman’ and ‘Steel’), Brussels sprouts (‘Gladius’, ‘Brigitte’ and ‘Maximus’) and swede (‘Vigod’, ‘Vige’ and ‘Neve’) using red light (RL) with wavelength of 600 nm and intensity of 10 μmol m2 s‑1 as a supplement to natural light. All seedlings were planted in an experimental field. Yield of the mentioned species and vitamin C content were measured after harvest. Night EOD treatment resulted in 7% shorter and more compact plants in broccoli (p=0.04). There were yield differences (31-44%) among cultivars within the cauliflower (p=0.001), broccoli (p=0.01) and Brussels sprouts (p=0.001). There were significant differences in vitamin C content among cultivars in all four Brassica species (p<0.01). This study provides new information about the effect of night break treatment with red light on seedling length in broccoli, yield differences in cultivars of cauliflower, broccoli and Brussels sprouts and on vitamin C content in different cultivars of four studied Brassica species.