Class B1 GPCRs are activated by ~30-40 amino acid polypeptide and are important targets for drug discovery for a variety of metabolic disorders. The endogenous hormones, while potent, are usually not ideal for therapeutic use due to metabolic instability. Here, we modified the peptide backbone of class B1 GPCR agonists with beta-amino acids, which impart protection from proteolysis and can tune receptor signaling profiles. We found that these backbone modifications can result in diverse activity, and we used electron cryo-electron microscopy to examine the structure and dynamics of the modified peptides bound to receptors and G proteins.