Public procurement is a cross-cutting government function of very high complexity and value, which underpins core government functions such as public service provision and public investment programs, but is highly vulnerable to corruption in many forms. Thus, the relatively rapid progress in recent years of the ‘open contracting’ movement, which advocates for governments to publish extensive data about the process, has been lauded as bringing major improvements in accountability and efficiency. However, most of the gains to date have been in relatively wealthy countries, with the state capacity and political will to invest in this rather technical reform. This research by contrast examines open contracting reforms in low and middle-income countries, providing a comparative analysis of de jure and de facto progress across nine countries in sub-Saharan Africa and Asia, and the underlying drivers of reform. Our results show a major implementation gap in most countries, but finds that the countries making most progress tend to be those which see open contracting largely as a route to improved efficiency and relief of fiscal pressure, with accountability emerging as an unintended byproduct. The paper concludes by outlining four advocacy strategies suitable for different political economy conditions.