Although principal investigators (PIs) are becoming key strategic actors in shaping new scientific trajectories, little is known about how they strategise in an evolving publicly funded research environment. Drawing on thirty interviews and extensive documentation from Ireland's science, engineering and technology (SET) sector, we take a closer look at the heretofore neglected strategic behaviours underlying the research activities of PIs. Our findings suggest that their strategic behaviours fall into four categories -research designer; research adapter; research supporter and research pursuer. We find that the mechanisms for selecting research strategies are interwoven with the posture (reactive/proactive) of PIs as well as their degree of conformance. We argue that more proactive PIs utilising non-conformance strategies shape new research trajectories, while conformative and/or more reactive PIs predominantly pursue and deepen existing trajectories. We discuss the wider implications of these findings for policy makers, funding bodies and the practicing PI and strategist.