Self-Regulated Strategy Development (SRSD) is a criterion-based teaching approach incorporating explicit and systematic instruction of writing strategies, knowledge or skills, and self-regulation procedures into writing. This study aims to estimate the overall average effect of SRSD on English writing outcomes and to examine the extent to which the effect was moderated by outcome features (writing outcome, genre, measure type), methodological features (assignment, duration of intervention, and methodological quality), learner features (educational level and country), and publication features (publication type). A total of 43 effect sizes were extracted from 22 primary studies that were published or written in the past decade. Results suggested that SRSD had a positively large effect on writing outcomes. Writing outcome type was found to moderate effect size estimates. SRSD had a statistically smaller effect on writing length than on quality and elements. In addition, published journal articles had significantly larger effect size estimates than dissertations. The current meta-analysis informs practitioners, classroom teachers, and program designers of the overall effect of SRSD on English writing and factors related to the effectiveness of SRSD interventions.