This study was designed to examine the reported and observed communication strategies used by Chinese English-as-an-additional-language (EAL) graduate students in electrical engineering and education in performing informal debate tasks. The strategies were elicited through strategy inventories, post-task strategy recalls, and task performances. The results revealed eight categories of communication strategies, with fluency-oriented strategies used most frequently and translation least frequently. Differences in using communication strategies were also found between advanced and high-intermediate learners, while the use of one individual strategy--clarifying stance--also notably differed between the two disciplines. Overall, results from nonparametric tests revealed significant positive relationships between certain categories of communication strategy use and learners' speaking performance. The findings and their implications are discussed both to inform practice and to encourage further research about the communication strategies used by EAL learners who are graduate students.