The purpose of this study was to determine whether third-grade teachers' instructional actions during reading comprehension lessons contributed to their students' reading comprehension achievement. Our framework focused on teachers' emphasis on three dimensions of instruction (pedagogical structure, teacher-directed instruction, and support for student learning), as observed in comprehension lessons across a year. Third-grade teachers' instruction was analyzed first by measuring their latent propensity to engage in instructional actions in the three dimensions and then by using these latent variables in a multilevel model to examine their students' gains in reading comprehension. Results provided support for the theoretical dimensions, taking into account contextual variables including lesson, student, and teacher characteristics; teachers' engagement in teacher-directed instruction and their support for student learning significantly contributed to their students' reading comprehension. Results suggest that analysis of teachers' instructional actions within and across lessons is a promising approach for the study of effective reading instruction. Appended are: (1) The Three Dimensions, as Represented by Specific Items and Examples; and (2) Survey Item Stems Included in the Models. (Contains 5 tables, 2 figures, and 2 footnotes.)