Liquid crystal NMR techniques were used to study an isotopically labeled lactam analog of ganglioside GM4 in an oriented bilayer system composed of L-α-dimyristoylphosphatidylcholine (DMPC) and 3-((cholamidopropyl)dimethylammonio)-2-hydroxy-1-propanesulfonate (CHAPSO). This discoidal bilayer system is used to mimic a biological membrane, the natural environment of GM4 and other glycolipids. Residual dipolar couplings (13C−13C and 15N−13C) and chemical shift anisotropy effects for the amide 13C and 15N labeled sites were measured in GM4 lactam, using both one- and two-dimensional NMR methods. The dipolar coupling data were interpreted using a torsional search for preferred geometry about the two elements of the glycosidic bond attaching the headgroup to the bilayer surface. This yielded three independent families of structures, all of which were consistent with the dipolar coupling data. An order matrix analysis was used to compare experimentally measured changes in chemical shifts upon orientation to those predicted by chemical shift tensors derived from ab initio calculations. One of the three families of structures was readily eliminated based on chemical shift measurements, and another was eliminated based on energetic considerations, leaving a single structure to represent the average conformation of the GM4 lactam headgroup at a membrane surface.