Rock chutes, rock riprap on steep slopes, are used as grade control structures to safely conduct a water flowto a lower elevation. Previous studies have reported relationships to predict the highest stable unit discharge on thesloping face as a function of the material D50 and the bed slope. However, the studies do not report the riprap sizerequired for stability at the toe of the chute. The riprap size required for outlet stability was examined in two separateflumes and two field-scale structures. For all tests, the D50 size predicted for stability on the sloping bed was also stableat the toe of the chute. The tailwater elevation resulting from the outlet reach and downstream channel resistance wassufficient to prevent movement of the riprap in the outlet reach.