Conformational changes of three cyclic beta-helical peptides upon adsorption onto planar fused-quartz substrates were detected and analyzed by far-ultraviolet (UV) circular dichroism (CD) spectroscopy. In trifluoroethanol (TFE), hydrophobic peptides, Leu beta and Val beta, form left- and right-handed helices, respectively, and water-soluble peptide WS beta forms a left-handed helix. Upon adsorption, CD spectra showed a mixture of folded and unfolded conformations for Leu beta and Val beta and predominantly unfolded conformations for WS beta. X-ray photoelectron spectroscopy (XPS) provided insight about the molecular mechanisms governing the conformational changes, revealing that ca. 40% of backbone amides in Leu beta and Val beta were interacting with the hydrophilic substrate, while only ca. 15% of the amines/amides in WS beta showed similar interactions. In their folded beta-helical conformations, Leu beta and Val beta present only hydrophobic groups to their surroundings; hydrophilic surface groups can only interact with backbone amides if the peptides change their conformation. Conversely, as a beta helix, WS beta presents hydrophilic side chains to its surroundings that could, in principle, interact with hydrophilic surface groups, with the peptide retaining its folded structure. Instead, the observed unfolded surface conformation for WS beta and the relatively small percentage of surface-bound amides (15 versus 40% for Leu beta and Val beta) suggest that hydrophilic surface groups induce unfolding. Upon this surface-induced unfolding, WS beta interacts with the surface preferentially via hydrophilic side chains rather than backbone amides. In contrast, the unfolded beta-hairpin-like form of WS beta does not irreversibly adsorb on fused quartz from water, highlighting that solvation effects can be more important than initial conformation in governing peptide adsorption. Both label-free methods demonstrated in this work are, in general, applicable to structural analysis of a broad range of biomolecules adsorbed on transparent planar substrates, the surface properties of which could be customized.