Students' engagement in writing mediates their academic literacy development as they become initiated and socialized into disciplinary communities. With a focus on the mediating role of writing, the present study investigates the ways in which two L2 students forge an early understanding of academic discourse when they carry out writing tasks across the curriculum as nonmajors. Using qualitative analysis, the research examined student writing in general education courses, course materials, and student interviews. The researcher analyzed data in search of developmental signs, that is, the points at which students acquired or reshaped their literacy practices according to disciplinary expectations. Study findings show that the features of writing tasks frame the ways in which students conceptualize disciplinary expectations, which manifested in three ways: Knowledge-telling, inferential search, and identity construction as a member. The relationship between academic literacy and writing tasks points to the importance of course materials and design, a variable to consider for improving instruction. Based on the findings, the present study discusses implications for teaching and research in L2 writing.