This study assessed the effects of three different intervention programs on low-SES mother-child joint activities and on their kindergarten-age children's progress in early literacy and language. Parents in three groups (119 mothers, 5 fathers) were coached to mediate child learning, respectively, in: interactive storybook reading, writing, or visuomotor skills. A group-specific workshop was followed by 7 weeks of tri-weekly structured dyadic interactions and weekly tutorial home visits. A fourth group (control) received no intervention. Results showed implementation success: Mothers coached in interactive storybook reading or writing mediation improved in the coached activity from pretest to immediate posttest and to delayed posttest. Interactive storybook reading improved less for older than younger children, whereas writing mediation improved more for older than younger children. No transfer emerged from one activity to the other: Coaching on reading had no effect on writing or visuomotor skills, and coaching of writing had an effect only on writing. Children's alphabetic skills were enhanced in the writing mediation-coached group, whereas linguistic competencies, unexpectedly, were not enhanced in the interactive storybook reading-coached group. The significance of writing mediation as a dyadic activity promoting literacy is emphasized.