Technical Abstract: Organic dairies face many challenges, one of which is the high cost of purchasing organic feed grains. Many of these farms are seeking lower-cost feed ingredients that can be reasonably fed to lactating dairy cows. Molasses seems to be a viable, less expensive source of supplemental energy and vitamins. However, anecdotal results have been mixed for farms that have used molasses as the sole energy source. This could be due to a variety of management or feed quality factors, but it is not currently known which factors have the greatest influence on success, failure, and those in between. This research project quantified milk production and other animal performance measures on an organic dairy farm in central New York that has fed molasses for two grazing seasons. In 2008, 1.36 kg DM of molasses and 0.45 kg DM corn-based grain mix was fed to a mixed-breed herd of organic dairy cows. In 2009, molasses intake was decreased (averaging 1.10 kg DM/cow/d across the grazing season) while corn intake was increased (1.00 kg DM/cow/d) in response to low body condition scores, the potential for greater milk production, and changes in milk to feed ratio. Milk production and milk fat were similar across both years, while milk protein was greater in 2009. Milk urea nitrogen (MUN) levels were greater than recommended throughout the grazing season, primarily due to the high level of soluble protein and rumen degradable protein found in pasture. Body condition score (BCS) was higher in 2009 compared to 2008 and the rate of BCS loss was slower in 2009. When the diets were analyzed using the Cornell Net Carbohydrate and Protein System (CNCPS), energy was the first limiting factor for milk production. In general, actual milk production mirrored that of CNCPS predictions in both years. The CNCPS predictions for MUN were variable compared with actual MUN values, suggesting variation in the ability of cows to efficiently utilize pasture protein. Income over feed costs (IOFC) was greater in 2008, primarily due to higher milk prices and lower corn feeding. In the current study, decreasing molasses and increasing corn meal in the second year (2009) did not result in greater productivity or profitability compared with greater molasses supplementation (2008). However, indicators of animal health and nutritional efficiencies such as BCS and milk protein content were slightly improved in 2009. Although profitability did not improve, if prices had remained constant over the two years, a greater IOFC may have resulted. Therefore, cost of molasses in relation to corn meal is an important determinant in making feed ration decisions. Additionally, animal health and productivity must be monitored closely to evaluate success of molasses supplementation.