Technical Abstract: Laminitis, a disease that causes lameness in horses, is thought to result from grazing on grass high in carbohydrates. Consequently, knowing the amounts and types of carbohydrates in a pasture may help horse owners to manage grazing in a way that reduces the risk of laminitis. This study describes the analysis of carbohydrates in orchardgrass collected near the Southern Piedmont Agricultural Research and Extension Center (Blackstone, VA). Orchardgrass samples were collected one day a week, in both morning and evening, for 8 weeks (April-June). In this way, diurnal as well as seasonal changes in carbohydrates could be followed. Upon collection, part of the sample was frozen on dry ice, and part was air-dried to simulate hay production. Carbohydrates were extracted by boiling samples in water and separated by high-performance liquid chromatography (HPLC) with electrochemical detection. In both frozen and air-dried tissue, fructans (fructose chains of varying lengths), were most abundant in the early spring. Also, on the earliest collecting date, fructans were significantly higher in the evening than in the morning. Glucose and fructose content did not differ significantly in morning and evening samples, but these sugars were significantly higher in frozen than in air-dried tissue. Sucrose, while barely detectable in fresh tissue, was the dominant simple sugar in air-dried tissue, and generally more abundant in evening than in morning samples. These results indicate that in orchardgrass, the simple sugar composition of hay differs greatly from that of pasture. Also, season and time of day can affect the types and amounts of carbohydrates taken in during grazing.