We have studied the size-selective reactivity of AlnBm- clusters in = 1,2 with O-2 to investigate the effect of congener substitution in energetic aluminum clusters. Mixed-metal clusters offer an additional strategy for tuning the electronic and geometric structure of clusters and by substituting an atom with a congener; we may investigate the effect of structural changes in clusters with similar electronic structures. Using a fast-flow tube mass spectrometer, we formed aluminum boride cluster anions and exposed them to molecular oxygen. We found multiple stable species with Al12B- and Al11B2- being highly resistant to reactivity with oxygen. These clusters behave in a similar manner as Al-13(-), which has previously been found to be stable in oxygen because of its icosahedral geometry and its filled electronic shell. Al-13(-) and Al12B- have icosahedral structures, while Al11B2- forms a 1 distorted icosahedron. All three of these clusters have filled electronic shells, and Al12B- has a larger HOMO-LUMO gap due to its compact geometry. Other cluster sizes are investigated, and the structures of the AlnB- series are found to have endohedrally doped B atoms, as do many of the AlnB2- clusters. The primary etching products are found to be a loss of two Al2O molecules, with boron likely to remain in the cluster.