This article looks at a teacher trainer development programme designed in response to the shift from Malay-medium to English-medium instruction in Malaysian secondary maths and science teaching. The programme presented a group of 25 Malaysian maths and science teachers with principles and methods from teaching English to speakers of other languages (TESOL). The immediate aim was to prepare them to design and implement an in-service workshop for other maths and science teachers by focusing on task-based learning and teaching (TBLT). At the interim point in the programme, written assignments and classroom observations showed that the teachers had begun to understand the value of tasks for teaching content in English.