Purpose: Persuasive communication skills are vital for achieving success in school, at work, and in social relationships. To facilitate assessment of persuasive discourse, we developed a clinically feasible persuasive speaking protocol and used it to compile a database of language samples. This database allowed us to describe the properties of adolescents' persuasive speaking skills. Method: We collected spoken language samples from 179 typically developing students in Grades 8-12, recruited from the United States and Australia. Participants were asked to persuade an authority figure to make a change in a rule or policy. Results: Language performance data reflecting both microstructural and macrostructural properties of spoken language were summarized and broken down by grade. We completed a factor analysis that documented three latent variables (syntax, discourse difficulties, and content). To test the validity of the persuasive measures, a subset of the participants completed an additional battery of assessments, which revealed weak to moderate relationships between the persuasive measures, general language ability, and working memory. There was no significant relationship between the persuasive language measures and an assessment of personality. Conclusion: Our persuasive language sampling protocol facilitated the collection of valid language performance data. The summary data can be used as benchmarks for clinical evaluations of adolescents suspected of having language difficulties.