Introduction: A large-scale bushfire is a complex decision environment, in which firefighters and fireground commanders must respond to uncertain and changing conditions. In this situation they need to manage multiple (often competing) cognitive demands, and they use metacognitive skills to keep their thinking on track. However, when things go wrong, fire agencies often respond by developing lengthy policies and procedures (such as SOPs), with the aim of avoiding such errors in the future. Indeed, this reduces the likelihood of some errors, but it can actually exacerbate the likelihood of others, because one of the underlying causes of human error is cognitive overload. Method: This research used human factors interviews on the fireground, and visual-cued recall interviews during simulations, to explore how expert career and volunteer bushfire fighters keep their thinking on track during a large-scale bushfire (Frye & Wearing, 2011¹ ). Results: The research shows that some rule-based procedures reduce errors (and increase safety), because they reduce cognitive load (eg ‘you just do it’). However, adherence to other rules and procedures can increase errors (and erode safety), because people fail to adapt to the current situation (eg ‘you really need to think about that’). Conclusions: This paper provides a model, and examples, of how experts build situational awareness, make decisions, put decisions into action, and adapt to changing conditions. In particular, the model describes how they keep their thinking on track, and avoid errors associated with cognitive overload, during large-scale bushfires in Australia.