A threshing device for harvesting machines having a cut front header for cutting plants to be harvested. The threshing device includes a feeder rotor, at least two threshing rotors, and a grille located underneath of the threshing rotors. The threshing rotors are placed adjacent to each other and only one is located adjacent to the feeder rotor. The feeder rotor feeds the plants to the threshing rotor nearest the feeder rotor. The grille runs continuously through all the threshing rotors and includes a plurality of waves parallel to each other and defining peaks and valleys. The valleys match the peaks of the adjacent waves. On each valley the corresponding threshing wheel is located.