Buckling and postbuckling behaviors of graphene platelet (GPL)reinforced dielectric composite beams are investigated through theoretical formulation. The effective material properties of the GPL reinforced composite (GPLRC)as required for structural analysis, i.e. tensile modulus, dielectric constant and Poisson's ratio are obtained by using effective medium theory and rule of mixture. Governing differential equations for the composite beam are established through Timoshenko beam theory, von Kármán nonlinear strain-displacement relationship and principle of virtual work. Governing equations are numerically discretized and solved by employing differential quadrature method (DQM), through which several parameters affecting the buckling performances are quantitatively identified. The results demonstrate there exists a critical GPL concentration, above which the electrical field significantly affects the beam's buckling and postbuckling behaviors. The dielectric beam's buckling performances are very sensitive to AC (alternating current)frequency within a certain range. Moreover, it is found the dielectric beam's buckling and postbuckling performances comprehensively depend on the concentration and aspect ratio of GPLs. The present work is envisaged to provide guidelines to develop GPL-based smart composites and structures.