The field of early autism research is in dire need of outcome measures that adequately reflect subtle changes in core autistic behaviors. This article compares the ability of a newly developed measure, the Brief Observation of Social Communication Change (BOSCC), and the Autism Diagnostic Observation Schedule (ADOS) to detect changes in core symptoms of autism in 44 toddlers. The results provide encouraging evidence for the Brief Observation of Social Communication Change as a candidate outcome measure, as reflected in sufficient inter- and intra-rater reliability, independency from other child characteristics, and sensitivity to capture change. Although the Brief Observation of Social Communication Change did not evidently outperform the Autism Diagnostic Observation Schedule on any of these quality criteria, the instrument may be better able to capture subtle, individual changes in core autistic symptoms. The promising findings warrant further study of this new instrument.