The aim of this work is to investigate the competition between energetic stabilization and surface morphological effects that lead to changes in CH3ONO conformer abundance ratios between the gas phase and different low-temperature matrices. Gaseous CH3ONO was analyzed to confirm the room-temperature cis and trans conformer abundances in the bath gases before deposition into the matrix chamber. Upon condensation of the room-temperature CH3ONO in three different matrices-N2, Ar, Xe -the cis and trans conformer abundances are seen to change in varying amounts, but always favoring an increase in the proportion of the cis conformer. Furthermore, when the angle of deposition is changed, we see additional changes in the conformer abundances. Quantum chemistry calculations of the 1:1 complexes help to uncover the effects of relative energetic stabilization and relative size of the conformers.