A study investigated linguistic, rhetorical, and strategic variables of the writing processes and products of 3 groups of graduate and undergraduate students: 28 native English-speaking Americans; 28 Koreans studying in the United States; and 90 Korean students in Korea. The last two groups were learners of English as a Second Language (ESL). Data were drawn from persuasive writing assignments, follow-up questionnaires about the writing process, and writing background and attitude surveys. Writing samples were analyzed for 10 linguistic variables (length variables, cohesion variables, discourse markers), 13 rhetorical variables (coherence variables, openings, closings, rhetorical questions, reader inclusion, counterarguments), and 12 strategic variables (outline, revision, writing confidence, writing attention, discourse knowledge use, audience awareness). Results indicate significant differences in process and product variables between native and non-native advanced writers and between non-native advanced and basic writers, which were significant predictors of writing quality. These variables were distributed across linguistic, rhetorical, and strategic categories suggesting that writing quality depends on all three groups of variables. Implications for ESL writing instruction are drawn. Contains 34 references. (MSE)