Technical Abstract: Onions (Allium cepa L.) generally are harvested based on percentage of tops broken over. Since plant metabolism changes over time, percentage of tops broken over may be used to determine a harvest time to deliver marketable bulbs with the best nutrient content. The cultivars Candy and Texas Grano 1015 Y were harvested at 10, 20, 30, 40 and 50% breakover in 2006 and 2007. Larger and heavier bulbs were produced by 'Candy' and in 2006, the year with near normal precipitation. There was little difference in bulb size and weight due to percent breakover. Bulb nutrient content was affected by year with the majority of nutrients being higher in 2006, and there were either no differences due to cultivar, or where differences were found nitrate-N, phosphate and sulfate contents were lower in 'Candy.' Soluble solids content was lower in 2006 and higher in 'Candy.' Content of nitrogen and phosphorous in a Kjeldahl digest; nitrate-N, phosphate, potassium and sulfate were either linearly or quadratically distributed over percent breakover. Nitrite-N, calcium, magnesium, sodium and soluble solids were randomly distributed over percent breakover. Bulb size and weight did not change from the 20% breakover point, and most nutrients, with the exception on nitrate- and nitrite-N, were highest below the 30% breakover. It appears that a harvest occurring soon after breakover begins would be beneficial in terms of nutrient content without loss of bulb size or weight.