We report on a proposal to reduce the group velocity of a small "laser" Bose-Einstein condensate upon passing through a larger "medium" condensate of the same isotopic species in analogy to slowing of light passing through dispersive media. We make use of ultracold collisions near a magnetic Feshbach resonance, which gives rise to a sharp variation in scattering length with collision energy and thereby changes the group velocity. A generalized Gross-Pitaevskii equation is used to derive an expression for the group velocity in a homogeneous medium as well as for the spatial delay delta, through a finite-sized medium BEC with a Thomas-Fermi density distribution. We predict a maximum reduction of the group velocity by a half, which physically corresponds to freely propagating Feshbach molecules. For typical narrow Feshbach resonances and a medium with number density 10(15) cm(-3), up to 85% of the lower bound can be achieved, making the effect experimentally observable. We also derive constraints on the experimental realization of our proposal.