A core tenet of the model of domain learning is that learning is shaped by cognitive and motivational forces. In writing, these catalysts include learners' knowledge, motivation, strategic behaviors, and skills. This study tested this proposition at two time points (Fall and Spring) with 179 fifth-grade students (52% were girls), examining if writing knowledge, motivation, strategic behavior, and skills each made a statistically significant and unique contribution to predicting writing quality and output on social studies persuasive writing tasks, after variance due to the other catalysts and reading comprehension were first controlled. Three of the four catalysts (writing knowledge, strategic behaviors, and skills) each accounted for statistically significant and unique variance in predicting writing quality, number of words, or both at each assessment point. These findings provided partial support for the model of domain learning as applied to writing.