The use of online language corpora in L2 teaching and learning is gaining momentum largely because corpora are an easily accessed source of language input that potentially provide rich and authentic lexico-grammatical data. This can be of particular use for students' writing as its incorporation can enhance the appearance of native-like fluency. We describe a particular online web-derived corpus constructed by means of digital library software, and we describe the nature of the concordancer that services it. This is a system we have named FLAX (Flexible Language Acquisition). Because the system incorporates not only a useful and authentic corpus but also linked databases, we maintain that it meets the need for an easily accessible online resource that gives explicit information about typical lexical and syntactic collocations. While online corpus-based resources are becoming more readily available, and their effective incorporation into language teaching is being documented, we seem to know little about how learners access them and make use of the results they generate. This paper reports on an exploratory investigation of the search strategies used by learners in a university general English course as they make use of FLAX, tracking the way they exploit the search results in their texts, and presenting their relevant comments about the system. In such a way, we seek to explain variation in students' use and effectiveness of search strategies to support their writing. This type of research, although exploratory, is critical if we are to acknowledge the need for students to become "research workers".