The present study explores four L2 mature writers' development of writing and voices in English between different academic environments, and seeks to create more meaningful grounds for teaching academic ESL writing in the U.S. and college writing in Taiwan. The approach of this study is influenced by Hirvela and Belcher's (2001) reading of terms they define as voicist--in other words, terms that refer to voices and identities. Qualitative research methodology is adequate for this exploratory study because of its capacity to gain in-depth and interpretive understanding of the composing process that second language writers employ in different contexts. The study results have highlighted some of the major challenges of academic writing Taiwanese L2 writers encounter when studying abroad at graduate level. One of the salient problems is inadequate academic writing skills, and the sub-problem is a failure to express ideas with a strong individual voice and to position themselves appropriately in their texts (e.g. having a narrow scope of positioning themselves, applying limited linguistic features to position themselves and lacking confidence to express their ideas and to position themselves in texts). As a result, they face great challenges in the Western educational system, but with their development of academic writing skills, voice, critical thinking through academic writing practices, L2 writers can overcome the challenges and become successful writers which can in turn lead to successful academic careers and publishing.