A rotating cylinder is used with a complementary fixed concave in a combine to separate grain from the leafy portion of the plant. The elongated cylinder is comprised of a plurality of aligned star-shaped hubs disposed in a spaced manner along its length. An elongated, linear raspbar is attached to each "point" of the aligned star-shaped hubs and extends the length of the cylinder for engaging and urging the plant against the concave and separating the grain from the plant's leafy portion. A flat elongated filler plate is disposed between each pair of adjacent raspbars for preventing the grain and crop residue from entering the hollow cylinder and for displacing the grain and crop residue rearwardly along the concave where it is discharged onto another combine grain processing and separation stage. The flat profile of the filler's plate prevents the grain and crop residue from remaining on the surface of the rotating cylinder for improved grain threshing. The fixed concave includes a plurality of spaced cross bars extending the length thereof and has a tapered profile in proceeding from front to rear. In addition, the spacing between adjacent cross bars of the concave decreases in proceeding from the front, or intake, end of the concave towards its rear, or discharge, end. The increased thickness of and greater separation between adjacent cross bars at the concave's intake end provide improved grain/crop residue separation, while the reduced concave thickness and reduced cross bar separation at its discharge end facilitates crop residue discharge.