G Protein-Coupled Receptors (GPCR) are targets for around 30% of all FDA approved drugs. Conversely, over 85% (>310 receptors) of the family remain undrugged, often despite clear linkage to disease. Important reasons for this are that high-throughput screening has failed to deliver optimal drug leads and a lack of structural knowledge about how ligands engage GPCRs has hindered compound optimisation. The neurotensin receptor 1 (NTS1) is a GPCR for the tridecapeptide neurotensin (NT). Activation of NTS1 by NT has been implicated in schizophrenia, Parkinson’s disease and hypothermia, as well as progression of certain cancers and drug abuse. Crystal structures of NTS1 bound to fragments of NT, as well as mutagenesis data, have defined intermediate states of NTS1 along with the high affinity binding site for NT. It is desirable to complement these achievements by probing the binding mode of NT in solution. Furthermore, little is known about transient interactions that underlie NT binding. Cellular high-throughput encapsulation, solubilisation and screening (CHESS)-based directed evolution, yielded stable and signalling competent mutants of NTS1 suitable for solution NMR studies. Saturation transfer difference (STD) NMR, a technique commonly used for fragment screening against soluble proteins was applied to map the binding epitope of the low affinity NT peptide NT10-13 to samples of NTS1 mutants expressed to the E. coli inner membrane and reconstituted in n-dodecyl β-D-maltopyranoside (DDM) micelles. Analysis of STD spectra enabled epitope mapping of the NT10-13/NTS1 interface. The epitope maps generated are in good agreement with molecular dynamics (MD) simulations of NT10-13 bound to our NTS1 variant. Our microsecond timescale MD simulations indicate that in solution, the Y11 of NT10-13 may adopt two main sidechain conformations of which only one was evident from previously published crystal structures. This work marks an important step towards elucidating the binding pathways of peptide GPCR ligands.