The impact of a 6-week summer Computer Based Resource Unit writing workshop was investigated with 60 third-year preservice teachers during 1 year and 100 similar teachers during year 2. Thirty experimental Ss in the year 1 workshop focused on understanding individual differences with 30 objectives, 217 content items, 343 instructional activities, 273 materials suggestions, and 197 measuring devices. Both workshop and control Ss later were rated by supervising teachers and independent raters (for eliciting student participation with verbal behavior) during practice teaching assignments. Results of testing indicated significant improvement by workshop Ss in cognitive content (ability to identify and write objectives and prescribe strategies) and in self-concept, improvement in utilization of curriculum and classroom management strategies, and no significant difference resulting from verbal interaction. In the second year replication study, different instruments were used with 30 different experimental and 10 prior control (control/experimental) Ss in the workshop, and a control group consisting of 30 different control, 10 prior experimental (experimental/control), and 10 prior control (control/control) Ss. Ten prior experimental (experimental/experimental) Ss had a 1-week refresher workshop. Results indicated that experimental Ss scored significantly higher than controls on an instruction measurement instrument and lesson planning. Longitudinal results showed that control/experimental and experimental/experimental Ss tended to rank higher than control/control and control Ss. (Appendixes give instrument sample and procedures.) (MC)