This presents an equivalent transmission-line circuit that accounts for the scattering of a TE polarized plane wave that impinges obliquely on a periodic array of metallic patches sandwiched in a dielectric slab. The proposed approach gives a very efficient reduced-order model of the electromagnetic phenomenon able to reproduce all the fine quantitative details of the reflection/transmission spectrum. Also, our model provides an easy theoretical frame to predict and/or understand all the qualitative behavior of the scattering when both oblique incidence and dielectric slabs are considered.