The enthalpies of formation for solid ionic nitrosonium oxalate, [NO](2)[O2C-CO2], nitronium oxalate, [NO2](2)]O2C-CO2], as well as covalent bis(nitroso)oxalic acid, ON-O2C-CO2-NO, and oxalic acid dinitrate ester, O2N-O2C-CO2-NO2, were calculated using the complete basis set (CBS-4M) method of Petersson and coworkers to obtain very accurate energies For the mtrosonium species, the ionic form a ([NO](2)[O2C-CO2]) was identified as the more stable isomer, whereas for the mtrosonium compound, the covalently bound dinitrate ester (O2N-O2C-CO2-NO2) was found to be more stable The combustion parameters with respect to possible use as ingredients in solid rocket motors for both stable species were calculated using the EXPLO5 and the ICT code The performance of an aluminized formulation with covalently bound dinitrate (O2N-O2C-CO2-NO2) was shown to be comparable to that of ammonium perchlorate/aluminum. This makes oxalic acid dinitrate ester a potentially interesting perchlorate-free and environmentally benign oxidizer for solid rocket propulsion.