Background: Contemporary research in composition studies emphasizes the constitutive power of genres. It also highlights the prevalence of the most common genre in students’ transition into advanced college writing, the argumentative essay. Consistent with most research in composition, and therefore most studies of general, first-year college writing, such research has primarily emphasized genre context. Other research, in international applied linguistics research and particularly English for Academic Purposes (EAP), has focused less on first-year writers but has likewise shown the frequent use of argumentative essays in undergraduate writing. Together, these studies suggest that the argumentative essay is represented more than other genres in early college writing development, and that any given genre favors particular discourse features in contrast with other genres students might write. A productive next step, but one not yet realized, is to bring these discussions together, in research that uses context-informed corpus analysis that investigates students’ assignment contexts and analyzes the discourse that characterizes the tasks and genres students write. This study offers an exploratory, context-informed analysis of argumentative and explanatory writing by first-year college writers. Based on the corpus findings, the article underscores discourse as an integral part of the sociocognitive practices embedded in genres, and accordingly considers new ways to conceptualize student writing genres and to inform instruction and assignment design. Research questions: Four questions guided the inquiry: What are the key discursive practices associated with annotated bibliographies and argumentative essays written by the same students in the same course? What are the key discursive practices associated with visual analyses and argumentative essays written by the same students in the same course? What are the key discursive practices associated with the two argumentative tasks in comparison with the two explanatory tasks? Finally, how might corpus-based findings inform the design of particular assignment tasks and genres in light of a range of writing goals? Methodology: The article outlines a context-informed corpus analysis of lexical and grammatical keywords in part-of-speech tagged writing by first-year college students across courses at a U.S. institution. Using information from assignment descriptions and rubrics, the study considers four projects that also represent two macro-genres: an annotated bibliography and a visual analysis, both part of the explanatory macro-genre, and two argumentative essays, both part of the argumentative macro-genre. Results: The corpus analysis identifies lexical and grammatical keywords in each of the four tasks as well as in the macro-genres of argumentative versus explanatory writing. These include generalized, interpersonal, and persuasive discourse in argumentative essays versus more specified, informational, and elaborated discourse in explanatory writing, regardless of course or task. Based on these findings, the article discusses the discursive practices prioritized in each task and each macro-genre. Conclusions: The findings, based on key discourse patterns in tasks within the same course and in macro-genres across courses, pose important questions regarding writing task design and students’ adaptation to different genres. The macro-genre keywords specifically inform exploratory sociocognitive “profiles” of argumentative and explanatory tasks, offered in the final section. These argument and explanation profiles strive to account for discourse patterns, genre networks, and purposes and processes—in other words, multiple aspects of habituated thinking and writing practices entailed in each one relative to the other. As discussed in the conclusion, the profiles aim to (1) underscore discourse patterns as integral to the work of genres, (2) highlight adaptive discourse strategies as part of students’ meta-language for writing, and (3) identify multiple, macro-level (e.g., audience), meso-level (paragraph- and section-level), and micro-level (e.g., discourse patterns) aspects of genres to help instructors identify and specify multiple goals for writing assignments.