The conformer abundance of CH3ONO was investigated using matrix-isolation spectroscopy. The next sections describe the methods in detail, which are summarized first: CH3ONO is diluted in one of three different bath gases-N2, Ar or Xe-and individual mixtures are deposited at varying angles onto a cold substrate where they form a low-temperature matrix at controlled temperatures. Spectroscopic analysis using a Fourier-Transform infrared (FTIR) spectrometer is employed. Conformer-specific vibrational bands in the infrared spectrum are integrated and compared to quantify the conformer abundance of cis-CH3ONO compared to trans-CH3ONO. These conformer abundances are compared with gas-phase measurements to determine the degree of change. Quantum chemistry calculations are performed to quantify binding energies between matrix-gas molecules and the two conformers of CH3ONO.