Macroscopic properties of CrOCN thin films are related directly to composition and property variations on multiple length scales. Compositions resolved on a nanometer scale were measured in-depth in 120–150 nm thick CrOCN films by sputtered neutral mass spectroscopy. A statistical analysis of composition identifies the particular coordinations of the various anions with Cr that form preferentially under relevant processing conditions. Near-edge structure in electron energy loss from transmission electron microscopy and the Cr core level shift in X-ray photoemission spectroscopy further support this conclusion. A wide range of compositions are described in terms of mixtures of binary and ternary compounds, and optical absorption is found to be correlated with the presence of Cr4+ within this description. It appears that the presence of the unfilled t2g state is responsible for optical absorption in the range of 0.5–6 eV and that a critical concentration of Cr4+ in certain species within the system is required for the transition to occur. These results conflict with the suggestion that a percolated network of metallic clusters is responsible for the change in properties.