This study planned to determine the differences among nutrient composition, in vitro digestibility, energy content, digestible dry matter and organic matter yields of barley forage harvested at three different stages of maturity. Each vegetation period (heading stage, seed formation stage and mature stage) was randomly assigned to 5 replication from 1 square meter area and fifteen samples were harvested in total. DM, ADF (p<0.001), and NDF (p<0.05) contents were different in each stages of barley forage. In vitro dry matter (IVDMD), organic matter digestibility (IVOMD), metabolizable energy (ME), and net energy for lactation (NEL) values of samples were determined to be lower than the other two stages at the mature stage (p<0.05). Yield parameters of barley were significantly affected by vegetation period (p<0.001). It can be concluded that all three vegetation period had significantly higher digestibility. Digestible DM, OM and energy yields were higher when harvested at the mature stage of vegetation.