This study investigated: 1) the influence of alphabet instructional content (letter names, letter sounds, or both) on alphabet learning and engagement of English only and dual language learner (DLL) children, and 2) the relation between children's initial status and growth in three underlying cognitive learning processes (paired-associate, articulation referencing, and orthographic learning) and growth in alphabet learning. Subjects were 83 preschool children in six public preschool classrooms with low-income eligibility thresholds, including 30 DLLs. Children were screened for alphabet knowledge and randomly assigned to small groups and one of four conditions: experimental letter names or letter sounds only, experimental letter names+sounds (LN+LS), or typical LN+LS. Research assistants provided nine weeks of instruction in each treatment, in 10-minute sessions, four days/week. Irrespective of language status, children in the four groups made significant growth from pretest to posttest on measures of alphabet learning. The single-focus letter name or letter sound conditions led to significantly greater growth on taught alphabet content. The experimental LN+LS condition led to greater growth in taught letter names and sounds content compared to the typical LN+LS condition. Pretest vocabulary and alphabet knowledge did not moderate growth, and only limited evidence of differential response to instruction among DLLs was found. Paired associate and articulation referencing learning processes were related to alphabetic growth. Engagement during learning was high in all four treatments. Findings support the benefits of explicit alphabet instruction that enlists cognitive learning processes required for alphabet learning. [This article was published in "Early Childhood Research Quarterly," v44 p257-274 3rd Quarter 2018.]