In response to calls for an assessment tool that provides a separate performance dimension from the linguistic quality-oriented measures of complexity, accuracy, and fluency (CAF) and guided by systemic functional linguistic (SFL) theories, this study introduces a set of fine-grained objective measures of communication/content/function (CCF)-related performance in second language (L2) narratives and empirically tests the validity of these measures using vigorous research procedures and statistical tests. The test results show that these CCF measures assessed their intended SFL functional dimensions, in contrast to the key CAF measures that evaluated mainly linguistic dimensions of narrative performance. More specifically, these CCF measures offered an objective evaluation of the communication/content quality of narrative task performance as evaluated by the subjective functional adequacy scales, while the key CAF measures provided an objective assessment of the linguistic quality of task performance as measured by the largely subjective International English Language Testing System (IELTS) scales. The study also discusses the implications of the results for making the assessment of L2 task performance more accurate and comprehensive.