The present study was concerned with eliciting information about the problems that bilingual or immigrant students' encounter and the strategies that they employ whilst writing in Greek as a second language (GL2) and in English as a foreign language (EFL). The sample consisted of a total of 32 bilingual students, aged between 10 and 12 from Albanian, Russian and Georgian families. The study followed a qualitative and quantitative method of data collection and analysis: (1) a screening writing test was used for student selection and their categorisation into skilled and less skilled writers; (2) student think-aloud reports and retrospective interviews were used to collect data whilst students were writing in GL2 and EFL. The findings indicated that the skilled bilingual writers held a much broader and complex view of their own writing process and showed more strategic knowledge compared to less-skilled writers. In particular, they were more flexible in using both cognitive and metacognitive strategies and employed a wider range of more 'elaborated' strategies. In contrast, the less-skilled writers had a more limited knowledge of the writing task, and they adopted lower-level processes and strategies. However, they had adequate awareness of their own writing problems related to word level, and they employed certain compensation strategies to overcome writing weaknesses. Some suggestions are made about the creation of educational and teaching conditions for developing bilingual students' linguistic cognitive and metacognitive skills and expanding opportunities for them to become autonomous writers.