This article reports a pilot study conducted in an EAP course for Colombian PhD students from different disciplinary fields at a private university. The study sought to identify the mechanisms to express originally written content in oral presentations (OPs), and how those mechanisms describe oral performance differences. To achieve these objectives, eight parallel pairs of texts (essays and their corresponding OPs transcriptions) were analyzed. Quantitative analyses were performed to complement the findings. Modifications to clause structure and heavily modified noun phrases were identified as two mechanisms to transition from written to oral discourses. These mechanisms are described in terms of the implemented resources, their pragmatic appropriateness, and their grammatical correctness. Topicalization and reduction of heavily modified NPs were useful sub-mechanisms to discriminate among levels of oral performance; other mechanisms like rhematization were not. This report also discusses the implications and limitations of the study, and the perspectives for future research.