Injectable peptide GLP-1 receptor (GLP-1R) agonists are highly effective anti-diabetic agents in clinical use. Constrained peptides with fewer polar side-chains were sought to facilitate oral bioavailability. Analysis of a potent 11 amino acid (11mer) peptide GLP-1R agonist by NMR and alanine scanning informed the design of conformationally constrained ligands that retained potent agonist activity. In addition, differences in the role of the N-terminal region of the 11mer peptide compared with GLP-1[7-36] were exposed. Further investigation of the N-terminal residue SAR led to the discovery of ligands with significant signaling bias between the cAMP and β-arrestin pathways.