A laboratory study was undertaken to determine the effect of grading/particle size distribution on permanent deformation in multi-stage repeated load triaxial (RLT) tests. Results showed the coarse gradings with a Talbot’s exponent n-value of 0.8 had the least amount of permanent deformation for high-moisture contents near saturation. Finer gradings with an n-value of 0.3 had the least deformation in all of the tests in dry conditions at less than 70% of optimum moisture content. Similar performance in terms of permanent deformation was obtained if variations of the n-value were less than 13%. Based on limiting the variations in n-value to ± 13% new grading envelopes for use in the new Transit New Zealand specification for RLT testing were proposed.