Our study tested whether learning is shaped by fundamental cognitive and motivational forces in the academic domain of writing. We examined whether strategic writing behavior and motivation (attitudes toward writing and self-efficacy) made a statistically significant and unique contribution to the prediction of writing quality and number of words written, after controlling for variance due to other components and gender. Overall, 227 fourth-grade students (120 girls, 107 boys) wrote a personal narrative story and completed instruments examining their strategic writing behavior and motivation. Strategic writing behavior and motivational measures accounted for statistically significant and unique variance in predicting writing quality. This was also the case for the motivation variables when number of words was the writing performance measure. These findings provided support for the model of domain learning as applied to writing. Both cognitive and motivational variables made separate and unique contributions to predicting the writing performance of young, developing writers.