<p>The Jeffrey fluid model is a well-established non-Newtonian framework, renowned for its ability to encode relaxation and retardation characteristics of complex fluids. Owing to this capability, it finds notable applications in polymer industries, physiological flows through arteries and pharmaceutical manufacturing. The present study investigates the periodic free convective Jeffrey fluid flow through a microchannel, under the combined influence of electric and magnetic fields, thermal radiation and internal heat source. The steric factor, arising from the finite volumetric occupancy of ions, is explicitly incorporated alongside large zeta potential conditions. Their combined treatment in oscillatory electro-osmotic magnetohydrodynamic Jeffrey fluid flow constitutes a novel contribution that remains unexplored in existing microfluidic transport literature. The non-linear electric potential distribution is described by the modified Poisson-Boltzmann expression. The governing set of equations for the conservation of momentum and energy along with the oscillating boundary constraints are modelled within the Boussinesq framework. The Runge–Kutta-Fehlberg method and the Caputo-Fabrizio fractional derivative approach are adopted to numerically resolve the coupled governing equations. A detailed parametric investigation is performed with a view to elucidate the influence of various parameters on the flow. Notably, increasing the steric parameter suppresses the velocity distribution due to the volumetric restriction of ions. Large zeta potential tends to deplete the available mobile ions, resulting in an overall reduction of velocity distribution. The numerical results are validated against existing literature to ensure the reliability of results.</p>