This research evaluated the effects of onion curing methods on the qualitative traits of Iranian onion cultivars (Azarshahr Red, Neishabour Red, Kashan White, Qom White). Testing was carried out in the autumn and winter of 2007. The experimental design was factorial with two factors and three replicates. The factors were traditional and sunlight curing methods at 42oC for 12 hr for 48oC for 4 hr and four onion cultivars. Bulb qualitative traits of firmness, sprouting percentage, total soluble solids content, vitamin C content and pyruvic acid content (pungency index) were recorded after four months storage. Results showed that onions stored using the different curing methods showed significant differences in firmness, weight loss, sprouting, vitamin C and pungency rate. Kashan White, Neishabour Red and Qom White demonstrated higher firmness. Bulbs cured at 42oC in sunlight had a higher rate of sprouting compared to those stored at 48oC. Pyruvic acid content in the sunlight method was higher than for the other method; the percentage of vitamin C was higher for onions cured at 42oC. Qom White onions cured solely in sunlight produced fewer losses and suitable quality traits, thus, this treatment is recommended.