While it is widely accepted that whole of hospital solutions are necessary to reduce the ever-increasing burden on the public health system, little research has focussed on understanding the relationship between ambulance arrival related flow metrics and emergency department (ED) crowding. Queensland Ambulance Service (QAS) shares patient load across multiple hospitals, and receiving facilities strive to meet a Patient Off Stretcher Time (POST) target of 30 minutes. We examine ambulance arrival data from the QAS and ED patient arrival data from 15 major metropolitan hospitals across Queensland, to understand temporal variations in POST performance and examine the relationship between POST performance and ED crowding. The findings suggest a relationship between ED occupancy levels and both ambulances waiting at the ED door and average POST at larger hospitals. No relationship between POST and ED length of stay was found, perhaps due to competing ED National Emergency Access Targets (NEAT). Further modelling is recommended to formally test these observations.