We investigate the Half-metallic ferromagnetism and optical behaviors of XBeO3 (X = Mg, Ca, Sr and Ba) using full-potential linearized augmented plane-wave method. The structural and thermodynamic stabilities are elucidated in terms of the calculated tolerance factor and enthalpy of formation, respectively. The room temperature (RT) ferromagnetism is shown by computing the Curie temperature and spin polarization. The strong hybridization between p-states of alkaline earth metals and 2p-states of oxygen near the Fermi level results total magnetic moment of 2 mu(B). The ferromagnetism occurs due to holes those result in the exchange interactions between the p-states of alkaline earth metals and oxygen. The potential optical applications are also suggested by computing the dielectric constant and refraction.