Abstract: A rotary baler is provided, front mounted on a self-propelled power unit, to ground roll cylindrical bales of fibrous material. A pick-up assembly at the rear of the baler lifts the fibrous material from the ground to engage a generally vertical rear belt assembly which moves the material upwardly. Rotating discs at the upper end of the rear belt assembly deflect the material forward to engage a forwardly extending upper belt assembly which biases the material forwardly. The upper belt assembly is pivotally mounted at its rear end so that it can rotate with the expansion of the forming bale. Flexible lengths of cable hang down forward of the upper belt assembly; these cables act to shape and contain the forward portion of the forming bale. A spring-biased arcuate arm assembly, positioned intermediate the upper belt assembly and the cables, guides and compresses the forming bale once it has reached a pre-determined size.