Establishing the test-retest reliability of these sensory brain responses in ASD was critical to their use as biomarkers of neural dysfunction in this population. To assess the degree of reliability of the variability of responses within individuals, analysis was performed on the variance of the measurements, in addition to their means. This yielded a total of 24 measures for which ICCs were calculated. The data paid significant-good ICC values for 10 of the 24 measurements. These spanned across behavioral and ERPs data, experimental conditions, and mean as well as variance measures. Measures of the visual evoked responses accounted for a disproportionately large number of the significant ICCs; follow-up analyses suggested that a greater number of trials to the optical compared to the auditory ERP partially accounted for this. This analysis reveals that sensory ERPs and related behavior can be highly reliable across multiple measurement time-points in ASD. The data further suggested that the inter-trial and inter-participant variability reported in the ASD literature likely represents replicable individual participant neural processing differences. The stability of these neuronal readouts supported their use as biomarkers in clinical and translational practice on ASD. Given the minimum interval between test/retest sessions across the cohort, it was also concluded that for the tested age range from 6 to 9.4 years, these reliability measures are valid for at least a 3-months interval. Limitations related to EEG task demands and going through the length in the context of a clinical trial are considered.