Through an English for Specific Purposes (ESP): Communication in Nursing online course design, the present study examines the efficacy of synchronous voice and text-based online chats as instructional and communicative modes in learning to use open questions for probing in therapeutic dialogues by non-native speaking (NNS) research study participants, students of a nursing college at a major university in the Philippines. Drawing upon a plethora of research findings in online education, the research study examines the following questions: (1) which interactional mode - voice or text - provides for better learning of probing questions by NNS medical professionals through noticing of their use in therapeutic dialogues and situations typical for everyday healthcare-related communicative settings in an online course; (2) is there evidence that the skill to use probing questions by NNS medical professionals developed through text-based practices in an online course might transfer to their speech and vice versa; (3) which interactional mode - voice or text - is perceived by the online-course participants as more effective for learning how to use probing questions in therapeutic dialogues