Food standards are jointly regulated in Australia and New Zealand under the Food Standards Code. However, country of origin labelling (CoOL) is one of the few divergences in these trans-Tasman food regulations. Australia has mandatory CoOL on many food products, while New Zealand does not. This difference raises questions regarding the most influential inputs into the policy process determining CoOL regulations. For policy advocates, this raises further questions of how to influence the decision-making process most effectively. Therefore, this research aims (1) to determine which factors of the policy process best explain the differing CoOL regulations in Australia and New Zealand and (2) to highlight aspects of the policy process that aid or impede the influence of policy advocates. To address these objectives, interviews were conducted among key stakeholders and relevant documents were analysed. The current findings reveal that an understanding of the policy networks in each country is necessary, but recognising the role of interests, ideas and institutions helps construct a comprehensive explanation of CoOL regulations. The characteristics of different network types are discussed as constraints or opportunities for promoting a group's position. Particularly, the structure of policy networks can help shape the way in which policy actors construct their argument and the audiences to whom this argument is directed.