The ground-state electronic structures of K₃V(ox)₃·3H₂O, Na₃V(ox)₃·5H₂O, and NaMgAl_1–xV_x(ox)₃·9H₂O (0 < x <= 1, ox = C₂O₄^2–) have been studied by Fourier–transform electronic absorption and inelastic neutron scattering spectroscopies. High-resolution absorption spectra of the ³Γ(t_2g²) → ¹Γ(t_2g²) spin-forbidden electronic origins and inelastic neutron scattering measurements of the pseudo-octahedral [V(ox)₃]^3– complex anion below 30 K exhibit both axial and rhombic components to the zero-field-splittings (ZFSs). Analysis of the ground-state ZFS using the conventional S = 1 spin Hamiltonian reveals that the axial ZFS component changes sign from positive values for K₃V(ox)₃·3H₂O (D ≈ +5.3 cm^–1) and Na₃V(ox)₃·5H₂O (D ≈ +7.2 cm^–1) to negative values for NaMgAl_1–xV_x(ox)₃·9H₂O (D ≈ –9.8 cm^–1 for x = 0.013, and D ≈ –12.7 cm^–1 for x = 1) with an additional rhombic component, |E|, that varies between 0.8 and 2 cm^–1. On the basis of existing crystallographic data, this phenomenon can be identified as due to variations in the axial and rhombic ligand fields resulting from outer-sphere H-bonding between crystalline water molecules and the oxalate ligands. Spectroscopic evidence of a crystallographic phase change is also observed for K₃V(ox)₃·3Y₂O (Y = H or D) with three distinct lattice sites below 30 K, each with a unique ground-state electronic structure.