We have shown here that using system-specific non-bonded force field parameters can result in accurate conformational preferences for short peptides. Rotamer populations and simulated J couplings for the dipeptide molecules are in good agreement with experimental data and compare favorably with the latest OPLS force field. For longer peptide molecules, the problems associated with fitting torsional parameters to a system-specific force field became more apparent. Using regularization in the fitting process was shown to overcome these issues and resulted in a J coupling error of just 0.90 ± 0.03 for the alanine pentapeptide. Further work investigating disordered peptides will ascertain how general this fix is.