Students with significant disabilities must participate in large-scale assessments, often using an alternate assessment judged against alternate achievement standards. The development and administration of this type of assessment must necessarily balance meaningful participation with accurate measurement. In this study, generalizability theory is used to estimate the dependability of reading items and tasks that have been administered using two formats of communication (receptive and expressive). The results reflect a trade-off between meaningful participation and accurate measurement of students with significant cognitive disabilities, particularly when considering the two formats. Significant variance is obtained for persons interacting with tasks, whereas the effect of raters is negligible. Furthermore, these results appear to vary across administrative format. (Contains 5 tables and 3 figures.)