ABSTRACT. Onion sets (small onion bulblets) may allow seed production with lower costs than the traditional biennial cycle. This research aimed to evaluate the seed-set-seed method for seed production of three onion cultivars grown in Uruguay. Small (16-21 mm) and large (26-31 mm) onion sets were evaluated in combination with four storage periods at 7°C (0, 15, 30 and 45 days) for the cultivars INIA Casera (IC) and Pantanoso del Sauce CRS (PS), and 0 and 30 days for INIA Valenciana (IV). Large sets produced higher yield for IC (1001 kg ha-1) and PS (745 kg ha-1) than small sets, with no influence of the cold period. Large set-size in combination with 30 days storage at 7°C showed the highest yield for IV (595 kg ha-1). Seed weight was only influenced in IC, with higher values for no cold storage and small sets with 30 days cold-storage. Germination in IV was higher for large sets with 30 days at 7°C, whereas in PS germination was higher for large sets with 15 days at 7°C. All treatment combinations showed germination higher than the 75% required in certification rules. Results suggest the viability of this method to obtain high quality seeds.