This randomized controlled trial with first- and second-grade students is the first experimental study addressing long-running disagreements about whether primary grade students should develop transcription and oral language abilities before learning to compose. It is also the first study at these grade levels to teach close reading (using science text aligned to the Next Generation Science Standards) to plan and write a timed informative essay. Theoretically and evidence-based multi-component writing instruction was developed, termed “Self-Regulated Strategy Development (SRSD) Plus.” SRSD Plus integrates evidence-based practices for transcription (handwriting and spelling) and oral language skills (vocabulary and sentence structure) with SRSD instruction for close reading to learn and then write informative essays. A total of 93 children in Grade 1 (n = 46, 50% female) and Grade 2 (n = 47, 51% female) in a high poverty school participated in the study (50% boys; mean age = 6.68; SD = 0.48). Students were randomly assigned to either teacher-led SRSD Plus or business-as-usual (writers workshop) condition within class in each grade. SRSD Plus was implemented with small groups for 45 min, three times a week, for 10 weeks. Outcomes examined included: instructional fidelity, spelling, handwriting fluency, vocabulary, sentence proficiency, discourse knowledge, planning, writing quality, structural elements in informative essays, number of words written, use of transition words, expository text comprehension, and use of source text. Results showed moderate to large effect sizes in writing outcomes, oral language skills (vocabulary and sentence proficiency), spelling, and discourse knowledge. Differential effects due to grade, gender, and race are examined, and directions for future research are discussed.