The requisite for a careful design of pavement subgrades and subbases has been stressed by the failures caused by fallacy in understanding the variability and uncertainty associated with material properties (Jung et al. 2012). This study emphasizes the improvement of California bearing ratio (CBR) found in the expansive soil after treating with lime and fly ash through probabilistic evaluation. The variability associated with the CBR values is studied for twenty soil specimens stabilized with lime and fly ash at varying proportions. A comprehensive analysis has been carried out in a probabilistic framework for a complete understanding of the variability range. The aftermath of the investigation can be suitably beneficial for a reliable and reasonably economical design of pavement subgrades.