An important component of fluent linguistic production and a key distinguishing feature of particular modes, registers and genres is the multi-word expressions referred to as ‘lexical bundles’. These are extended collocations which appear more frequently than expected by chance, helping to shape meanings and contributing to our sense of coherence and distinctiveness in a text. These strings have been studied extensively, particularly in academic writing in English, but little is known about how they may have changed over time. In this paper we explore changes in their use and frequency over the past 50 years, drawing on a corpus of 2.2 million words taken from top research journals in four disciplines. We find that bundles are not static and invariant markers of research writing but change in response to new conditions and contexts, with the most interesting changes within disciplines. The paper also discusses methodological approaches to studying bundles diachronically.