This trial compared two RUSF containing 500 calories and either 15% or 33% of dairy protein for 3 months vs. a wait-listed control. Each RUSF was provided 5 days per week. Changes in weight-for-age and height-for-age Z-scores (WAZ, HAZ) were the primary outcomes. Additional outcomes included mid-upper arm circumference (MUAC), hemoglobin and retinol binding protein levels and disease incidence. Z-scores increased significantly in all groups over baseline, but there was no significant effect of the RUSFs on changes in WAZ or HAZ. There was a significant effect of supplementation on the association between baseline WAZ and WAZ gain. There was a significant positive effect of the 33% dairy protein RUSF on change in MUAC . Reported rates of malaria decreased in children randomized to either supplement. This study provides the first evidence that RUSF with 33% versus the more typical 15% of protein provided by dairy may have particular benefit for prevention of wasting. It also indicates that RUSFs demonstrate growth benefits across the range of baseline anthropometric measures.