Given that more paraprofessionals are hired to deliver one-on-one intervention to children with Autism Spectrum Disorder (ASD) under the auspices of behavioral health agencies, it is important that these paraprofessionals receive adequate supervision to support their implementation of high quality intervention while often working alone without frequent observation and feedback from their supervisors. This study investigated a training package consisting of didactic training and performance feedback delivered via electronic mail as a means of improving behavior therapists' use of an evidence-based practice called instructive feedback (IF). A multiple baseline design across four behavior therapists was employed. The findings suggest that the training package was effective and efficient in improving behavior therapists' use of IF. However, only when e-mail feedback was given did the behavior therapists demonstrate proficiency of IF implementation. Maintenance and generalization across children, and social validity were also assessed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]