We present a numerical framework for modeling the temporal evolution of ground deformation caused by a subsurface, pressurized magma reservoir situated within a viscoelastic medium. The host rock surrounding an oblate, ellipsoidal magma reservoir behaves as a Maxwell material. Temporal evolution due to the viscous effects are encoded as source terms on the static equilibrium equations; the coupled system is solved via high-order FEM and explicit time-stepping. We derive numerically stable time steps and verify convergence at the theoretical rate. For an applied, sinusoidal pressure at the reservoir boundary, the model is shown to reproduce the theoretical relationship between stress and strain for Maxwell materials.