The Training and Assessment of Relational Precursors and Abilities (TARPA) protocol was developed to assess the emergence of derived relational responding, which has been argued by relational frame theory (RFT) to be the key process underlying language. Previous research showed a correlation between the TARPA and the Vineland Adaptive Behavior Scales (VABS) in several children with autism spectrum disorder (ASD). The current study advanced this work by correlating a more comprehensive and systematic TARPA protocol with the Preschool Language Scale, Fourth Edition (PLS-4), a mainstream performance-based language assessment, in 10 additional children with ASD (Experiment 1) and 13 typically developing children (Experiment 2). This study also involved a hierarchical analysis of the TARPA. Results showed (a) a strong and significant correlation between the TARPA and PLS-4 full scale and subscales, and (b) evidence to support the hierarchical structure of the TARPA. The implications of these and other findings are discussed.