Children's writing depends on strategic and self-regulated behaviors as well as on attention and transcription skills. Despite the well-established effectiveness of interventions based on the self-regulated strategy development model (SRSD), little is known about their effects when combined with the explicit teaching and systematic training of attention or transcription. This study compared the effects of SRSD interventions that taught students a planning strategy and how to use it compose text, with additional components of attention (via focused meditation exercises) or transcription (via copy and alphabet exercises). We used a quasi-experimental design with three groups of Portuguese third graders: SRSD + attention (n = 42), SRSD + transcription (n = 37), and wait list (n = 34). Measures of transcription, executive functions, motivation, written production, and academic achievement were collected before and after the interventions. Analyses of co-variance revealed that the SRSD + transcription group surpassed the others in terms of handwriting fluency as well as in terms of spelling accuracy, though only among the weakest spellers at pretest. Moreover, in comparison to the wait list group, both SRSD groups showed better planning skills, wrote more complete texts, and displayed better executive functioning at posttest. After the intervention, though the SRSD + transcription group produced better texts than their peers, the SRSD + attention group achieved better academic performance, but only among those with poorer grades at pretest. Regarding motivation, we only found an effect of the SRSD + transcription intervention on self-efficacy for ideation, among students with lower self-efficacy at pretest. These findings suggest the importance of articulating writing and self-regulation strategies with attention and transcription training in early schooling.