In the 3D network [Rh(bpy)3][NaCr(ox)3]ClO4 (ox ) oxalate, bpy ) 2,2'-bipyridine) phonon-assisted as well as resonant energy migration within the R1 line of the 4A2 f 2E transition of Cr3+ has been identified. The latter is dominant below 4.2 K, and in a fluorescence line narrowing spectrum, it manifests itself in a multiline pattern across the inhomogeneous line width with spacings corresponding to the zero-field splitting of the 4A2 ground state (Milos, M.; Kairouani, S.; Rabaste, S.; Hauser, A. Coord. Chem. ReV. 2008, 252, 2540). H. Riesen demonstrated efficient spectral hole burning within the R1 line of Cr3+ doped at low concentrations into partially deuterated NaMg[Al(ox)3] ·9H2O (Riesen, H. Coord. Chem. ReV. 2006 250, 1737). Here we show that at higher Cr3+ concentrations in the same host, both phenomena can be observed simultaneously, the resonant energy migration thus creating an additional series of persistent side holes.