This study provides initial evidence supporting intended score interpretations for the purpose of assessing opportunity to learn (OTL) via an online teacher log. MyiLOGS yields 5 scores related to instructional time, content, and quality. Based on data from 46 middle school classes, the evidence indicated that (a) MyiLOGS has high usability, (b) its quarterly summary scores are relatively consistent over time, (c) summary scores based on 20 randomly sampled log days provide reliable estimates of teachers' respective yearly summary scores, and (d) most teachers report positive consequences from using the instrument. Agreements between log data from teachers and independent observers were comparable to agreements reported in similar studies. Moreover, several OTL scores exhibited moderate correlations with achievement and virtually nonexistent correlations with a curricular alignment index. Limitations and directions for future research to strengthen and extend this initial evidence are discussed.