This study investigated micro- and macrostructural text features, and the impact of language-specific skills, on the bilingual, persuasive writing of 41 high school students learning English in Italy. Participants composed persuasive essays on 2 topics, each in Italian and English, and completed spelling and sentence generation tasks in both languages. Texts were assessed for fluency, productivity, complexity, and discourse quality. Repeated-measures analysis of variance was used to explore group differences between Italian and English writing. Correlations and regression analyses were used to investigate the impact of spelling and sentence generation on writing skills. Texts were more productive in English and more complex in Italian; however, no significant differences emerged between languages for fluency or discourse quality. In Italian writing, sentence generation skills affected only fluency. In English writing, spelling explained most of the variance in fluency and also impacted productivity, complexity, and quality. Results not only suggest cross-language transfer of discourse-level composition skills but also highlight the role of language-specific constraints in written text production.