Onions grown in New Mexico currently are hand-harvested. In order to remain competitive and to lower production costs, growers will need to harvest onions mechanically. The current recommendation for harvest time is when 80% of onion tops have fallen. The objective of this study was to measure several bulb quality traits when bulbs were harvested at four different stages. Twelve short- and intermediate-day onion cultivars of different maturities were sown during Sept. 2004 in Las Cruces, N.M. Bulbs were harvested at four stages of physiological maturity: 20% tops down (TD), 80% TD, 1 week after 80% TD, and 2 weeks after 80% TD. After curing, data on harvest date, bulb diameter, height, firmness, number of growing points, average center diameter, fleshy scale number, and thickness were collected. For most traits, no differences existed among the different treatments. For the earliest-maturing cultivars, the maximum bulb firmness and number of scales were observed when bulbs were harvested 2 weeks after 80% TD. For later-maturing cultivars, the maximum number of scales was observed 1 week after 80% TD, while the maximum bulb firmness was observed at 2 weeks after 80% TD. For latest-maturing cultivars, bulbs harvested at 1 week after 80% TD were firmer than bulbs harvested at other times. For later-maturing cultivars, average scale thickness was greatest when bulbs were harvested 2 weeks after 80% TD. From this work, a delayed harvest of 1 to 2 weeks after 80% TD resulted in firmer bulbs with more scales.