In recent years, cereals especially barley and oat grains have attracted researches and commercial attention mainly due to their high contents of dietary fibers, β- glucan and phenolic compounds with high antioxidant activates. Therefore, a preliminary study was carried out to estimate the components of raw barley and oat grains as well as, the effect of germination process on chemical composition and biological active compounds. The obtained results reveled that the germination process had a great role on the efficiency of chemical composition of selected cereal grains. A large number of negatively valued components in the grains such as crude fibers and starch contents of barley and oat decreased with prolonging the germination time process and the reduction of their contents due to the activity of α–amylase enzymes during germination process which led to an increase in total sugars. Phytic acid decline with germination time increase.   Otherwise, protein contents gradually increased with prolonging the germination period being 15.24 and 12.96% after three days for barley and four days for oat, respectively. Prolonging the germination time increased the minerals content of barley and oat grains and improved the bioavailability of essential minerals. Moreover, β –glucan contents declined with increasing the germination time process. Prolonging germination period increased total phenolic compounds, flavonoids contents and antioxidant activity, Catechin and pyrogallol were the major free phenolic compounds that existed in raw and germinated barley and oat grains. Nicotinic acid and Vit. B1 were the most abundant B complex vitamins in raw barley and oat grains and they highly increased during the germination period more than two folds recording 120.81 and 145.56 mg/100g & 335.21 and 441.62 mg/100g, respectively.        Finally, it could be concluded that germination process had positive effects to improve the bioactive compounds contents as total phenolic and flavonoids compounds, antioxidant activity and an increase in bioavailability of essential minerals and a higher content of Vit. B complex of barley and oat grains.