A processing system for a combine harvester has a tubular rotor housing that concentrically receives a rotor used for threshing and separating crop materials. Concave and separator grate assemblies are arranged side-by-side axially along the processing system. Each grate assembly has laterally spaced apart side rails and a plurality of axial bars spanning the side rails. Each axial bar has a plurality of fingers extending therefrom toward an adjacent axial bar, the fingers defining apertures through which grain may pass. Each axial bar additionally has a plurality of disrupter walls placed between adjacent fingers, wherein an upper edge of each disrupter wall projects above the fingers on the same axial bar such that it is closer to the rotor to disrupt the axial flow of the crop material through the rotor housing.
