Micro-macro scale transition theories were essentially developed to model the inelastic behavior of polycrystals starting from the local behavior of the grains. The anisotropy of the plastic behavior of polycrystalline metals was mainly explained by taking into account the crystallographic textures. Issues like plastic heterogeneities due to grain size dispersion, involving the Hall-Petch relation at the microscale, were not often taken into account in the literature, because only the role of a mean grain size was investigated. Here, the coupled roles of grain orientation and size distributions on the plastic deformation state of grains are examined for a tensile deformed IF steel in the light of EBSD experimental data based on misorientation parameters and of a micromechanics-based modeling regarding grain and overall behaviors.