Wehave investigated the structural, electronic, and optical properties of layered oxyhalides using plane wave pseudopotential and full-potential linearized augmented plane wave methods based on density functional theory. The structural properties calculated using local density approximation (LDA) are in reasonable agreement with the experiments compared to generalized gradient approximation (GGA) for these layered materials.Wefind these compounds to be wide band gap insulators with band gap ranging from 3.6 to 7.8 eV. The band gap decreases on moving from Cl to I, while it increases from the La to Lu series. The calculated refractive index show LaOCl and LaOBr to be optically isotropic in the lower energy regions in-spite of its anisotropic structure. From the present calculations, we predict bromides and iodides to be better scintillating host materials to exhibit Ceactivation among the studied compounds and especially lanthanum-based compounds are found to be more promising among the studied ones. © 2015 IOP Publishing Ltd.