- The S-parameters method for bi-anisotropic metamaterials effective constitutive parameters extraction is extended to oblique incidence. The proposed method enables to extract all unknown parameters using S-parameters measured over a single metamaterial slab. The bi-anisotropic metamaterial is a pseudochiral omega medium and assumed to have diagonal permittivity and permeability tensors. The extraction process suggested involves both analytical extraction equations and numerical optimization. This method is utilized to show the limited validity of the assumption of absence of spatial dispersion on which the proposed approach is based. The extraction method is demonstrated over bulk and artificial media such as SRR metamaterial and the results are validated with satisfactory agreement published data in the literature.