The G protein-coupled receptor (GPCR) autoproteolysis-inducing (GAIN) domain is a structurally conserved and tell-tale fold of class B2/adhesion GPCRs (aGPCRs). Self-cleavage of the GAIN domain is central for mechanobiological and signaling properties of aGPCRs. Biochemical analyses and atomistic details of several GAIN domain structures have recently provided a basic understanding on the molecular mechanism of the autoproteolytic reaction. However, if and how self-cleavage may be impacted by factors outside of the GAIN domain has not been systematically investigated. Here we used ADGRE2/EMR2 as a model receptor to explore processes contributing to the autoproteolytic cleavage of its GAIN domain. Retention Upon Selective Hook (RUSH), a quantitative pulse-chase assay to temporally follow newly synthesised receptor protein, showed that receptor self-cleavage serves a checkpoint function before exit of newly synthesised receptor protein from the ER, but not for plasma membrane trafficking. We established that autoproteolysis occured before or during synthesis of the first transmembrane helix, and that the extent of cleavage increases with the translation of the complete heptahelical (7TM) region of the receptor. We show that this effect is caused by tethering the nascent receptor to the lumenal side of the ER membrane during receptor biogenesis. ER membrane tethering facilitates GAIN domain processing by positioning the receptor near components of the N-glycosylation pathway, as demonstrated by genetic code expansion combined with biorthogonal labeling of the GAIN domain, photo-crosslinking and mass- spectrometric analysis. Collectively, these findings provide evidence that the extent of GAIN domain cleavage depends not only on intra-domain parameters, but can be modulated by the subcellular location of the domain, which aids its post-translational glycosylation. We anticipate that our findings will be valuable for understanding the GAIN domain self-cleavage of other aGPCRs, and will inform pharmacological strategies to modulate their activation and signaling.