Due to the heterogeneous distribution of chemical functionalities present on the surface of most proteins, adsorption to solid materials of differing surface chemistry may produce different bound molecular orientations. Differences in molecular orientation may in turn produce differences in adsorbed biofunction, which has important implications for fabrication of protein-based molecular devices. Aspects of this topic were addressed here by investigating molecular orientation in submonolayer to monolayer thick films of myoglobin (Mb) and cytochrome c (cyt c) adsorbed to hydrophilic and hydrophobic glass substrates. Orientation was determined by measuring the mean tilt angle of the heme moiety in protein films supported on a planar integrated optical waveguide. The results show (i) mean molecular orientation in monolayer films of both Mb and cyt c on both substrates is anisotropic rather than random (ii) molecular orientation in monolayer cyt c films is dependent on the wettability of the substrate and (iii) on both substrates, molecular orientation in submonolayer Mb films is substantially different than that in monolayer films.