Using formative design experiment, we engaged in iterative rounds of data collection, analysis, and redesign across three rounds to explore and hone 41 preservice-teachers' (PTs') preparation for selecting and integrating digital texts/tools in literacy instruction. Each PT submitted about two videos of literacy tutoring sessions (88 total). These were scored for quality using the DigiLit Framework rubric criteria. Multilevel regression modeling was used to explore potential changes in the quality across three rounds. Findings showed that shifts in literacy professor's pedagogy (sharing model videos of digital texts/tools integration) resulted in improved PT's practices (modeling literacy practices, modeling and guiding digital tool use, transformativeness). Further, findings underscore the importance of design experiments to uncover more effective teacher educator practices.