A tamper of a screed having an eccentric shaft including an eccentric section and an eccentric bushing rotatably mounted in a connecting rod driving a tamper bar. The stroke of the tamper bar is adjustable by a relative rotation between the eccentric shaft and the eccentric bushing, and a tappet and a preselection area with two tappet stop positions defining two different tamper bar strokes are provided between the eccentric shaft and the eccentric bushing, enabling adjustment of the tappet to each tappet stop position, by reversing the direction of rotation of the eccentric shaft to switch between the two strokes.