This study aimed to better understand what changes in underlying socioeconomic characteristics and behavioral factors are important in explaining improvements in child linear growth in A&T study areas in Bangladesh and Viet Nam. Oaxaca-Blinder regression decompositions were used to examine which underlying determinants contributed to HAZ changes over time and proved a useful and simple technique for analyzing nonintervention drivers of nutritional change in intervention and comparison areas. Improvements in underlying determinants explained rapid improvements in height-for-age z scores (HAZs) between 2010 and 2014 in Bangladesh and Viet Nam as further outlined in the article. A challenge in applying the decomposition technique to program design is that drivers that were important in the past may not be important in the future. The current levels of underlying determinants and the potential to improve them must be considered in deciding what investments to make. The decomposition findings, however, can be useful for showcasing successes in improving nutrition in select countries or regions and a powerful way of illustrating the importance of collaboration among various sectors to achieve nutrition goals. The analyses strongly suggest that nonintervention socioeconomic factors were important predictors of nutritional change in both comparison groups and in both countries meaning that improvements in nutrition-sensitive programs from a variety of sectors are needed to accelerate progress in improving nutrition globally.