Protein glycosylation is one of the most common post-translational modifications in eukaryotes and affects various aspects of protein structure and function. To facilitate studies of protein glycosylation, we paired glycosylation site–specific stable isotope tagging of lectin affinity–captured N-linked glycopeptides with mass spectrometry and determined 1,465 Nglycosylated sites on 829 proteins expressed in Caenorhabditis elegans. The analysis shows the diversity of protein glycosylation in eukaryotes in terms of glycosylation sites and oligosaccharide structures attached to polypeptide chains and suggests the substrate specificity of oligosaccharyl transferase, a single multi-enzyme complex in C. elegans that incorporates an oligosaccharide moiety en bloc to newly synthesized polypeptides. In addition, topological analysis of 257 N-glycosylated proteins containing a putative single-transmembrane segment, which were identified based on the relative positions of glycosylation sites and transmembrane segments, suggests that an atypical non-cotranslational mechanism translocates large N-terminal segments from the cytosol to the endoplasmic reticulum lumen in the absence of signal sequence function.