Proso millet (Panicum miliaceum) is an annual warm season grass that is usually grown for grain production. However, it also could be used as a forage crop. The objectives of this study were 1) to determine if proso millet could be grown as a forage crop in a cool and humid climate and 2) to determine the optimum harvest timing when underseeded with alfalfa. Two type of proso millet (red and gold) were seeded in 2010 and underseeded with alfalfa (cv. AC Caribou). There were four cutting stages: booting, first spikelet of inflorescence visible, beginning of anthesis, and ripening. The type of proso millet had no significant effect on forage yield and quality. Yields ranged between 788 kg DM ha^-1 to 3467 kg DM ha^-1 depending on harvesting stage. The harvesting stage of the proso millet had no effect on the productivity of alfalfa harvested in 2011.