We investigate mixing of a bidisperse distributions of spherical particles for slowly rotating vanes by pouring smaller beads, diameter d1, onto a monodisperse bed composed of larger beads, diameter d0, and monitoring the torque and lift forces. If the mixing beads are too small, d1/d0 < 0.05, the drag and lift are unaltered. Otherwise smaller beads displace larger beads from the shearing region, and if present in sufficient quantity both the drag and lift diminish to values of a monodisperse bed composed entirely of the smaller beads. We observe reductions in the torque up to 70%. The rate at which smaller beads leave the shearing region decreases as their size relative to the larger beads increases, and for d1/d0 > 0.155 the smaller beads remain inside the shearing region.