A numerical FLAC model was used to investigate the influence of vertical stiffness of the foundation on the performance of an idealized 6-m high reinforced soil modular block retaining wall. Three different Winkler linear spring values were used to simulate a rigid foundation and two compliant foundation cases. For each foundation condition, the influence of reinforcement material stiffness was also investigated. One material matched the properties of a relatively extensible polymeric geogrid product and the other a relatively inextensible welded wire mesh material with much higher stiffness but the same strength. The results of simulations show that as foundation stiffness decreases, reinforcement loads increase. However, for the two reinforcement materials in this study, the influence of axial stiffness of the reinforcement had a greater effect on wall performance than the foundation stiffness for walls subjected to operational (working stress) conditions at end of construction.