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Body centered cubic-derived intermetallic materials are promising candidates for applications in extreme environments, most notably as precipitate strengtheners and coating materials. Yet, the strong bonding schemes that stabilize the structure often lead to large elastic anisotropy, complex slip modes, and defect structures and hence plastic deformation mechanisms. Here, we examine the progress of plastic deformation in L21-ordered MnCu2Al by monitoring its evolution with Laue microdiffraction at room temperature and post mortem transmission electron microscopy. Our results reveal stable single crystal compressive plastic deformation at plastic strains up to 6.5%, at which point severe strain localization is observed. The orientation relationship of the crystal rotations is initially consistent with activation of the {110} slip mode, but transitions to the {112} slip mode with increased strain. This is consistent with our previous observations of the {110} slip mode in L21-ordered MnCu2Al with similar compressive loading to lower strains. We rationalize the discrepancy between these observations by examining ab initio generalized stacking fault energy calculations corresponding to {110} and {112} shear and through comparison with related BCC-derived intermetallics. Our work reviews the roles of deformation temperature, degree of chemical order, and total strain in the activation of different slip systems observed in L21-ordered MnCu2Al and motivates increased systematic study of the orientation, strain, strain rate, and temperature dependencies of deformation modes in BCC-derived intermetallic materials.