Background: While public health experts have identified food environments as a driver of poor diet, they also hold great potential to reduce obesity, non-communicable diseases, and their inequalities. Supermarkets are the dominant retail food environment in many developed countries including Australia. The contribution of supermarket own brands to the healthfulness of retail food environments has not yet been explored. The aim of this protocol is to describe the methods developed to examine the availability, nutritional quality, price, placement and promotion of supermarket own brand foods within Australian supermarkets. Methods: Photographic audits of all supermarket own brand foods present in three major food retail outlets were conducted. Two researchers conducted the supermarket audits in Perth, Western Australia in February 2017. Photographs showing the location of the in-store product display, location of products on shelves, use of display materials, and front-of-pack and shelf-edge labels were taken for each supermarket own brand food present. An electronic filing system was established for photographs from each of the supermarkets and an Excel database constructed. The following data were extracted from the photographs: front-of-pack product information (e.g. product and brand name, pack weight); packaging and label design attributes (e.g. country of origin; marketing techniques conveying value for money and convenience); shelf-edge label price and promotion information; placement and prominence of each product; and nutrition and health information (including supplementary nutrition information, nutrition and health claims, and marketing statements and claims). Nutritional quality of each product was assessed using the principles of the Australian Guide to Healthy Eating, the NOVA classification of level of food processing, and the Health Star Rating score displayed on the front-of-pack. Discussion: Approximately 20,000 photographic images were collected for 3940 supermarket own brand foods present in this audit: 1812 in the Woolworths store, 1731 in the Coles store, and 397 in the IGA store. Analysis of findings will enable researchers to identify opportunities for interventions to improve the contribution of supermarket own brands to healthful retail food environments. This protocol is unique as it aims to investigate all aspects of retail food environments and address the contribution of supermarket own brands.