Covert metalinguistic activity has received little attention in the field of second language (L2) education, even though the few studies that have examined this type of attention to language note that it plays a role in L2 learning and use. However, little is known about this phenomenon. The study reported in this article focuses on the knowledge representations at the basis of covert metalinguistic activity. The interaction of seven groups of bilingual learners writing collaboratively in their L2, English, was analysed into language-related episodes (LREs). The data show that turns with explicit knowledge of language occurring in covert LREs may constitute evidence that the knowledge representations underlying this form of attention to language are likely explicit (i.e. conscious and potentially verbalisable). Further support for this working hypothesis comes from arguments found in related literature about explicit knowledge. The article emphasises the need for further research on this type of metalinguistic activity and discusses methodological approaches that might help confirm this hypothesis, as well as pedagogical implications. (Contains 2 tables and 6 notes.)