Corporate environmental reporting (CER) plays important role due to the increase in public awareness of environmental issues. Hence, to be beneficial, corporate managers should not merely display CER information but rather emphasize on the quality of information disclosed. The quality of CER can be seen as a key value for companies and many benefits could be provided if companies released high quality environmental information. Prior environmental disclosure literature has not focused much on disclosure quality; instead, it concentrated on the quantity of disclosure. In addition, most of the few studies that focused on quality of environmental disclosure have revealed low level of quality of such disclosure. Therefore, this study aims to investigate the quality of environmental disclosure in different reporting mediums by oil and gas companies in developing countries. Using content analysis, an index and scoring scheme were applied to the annual reports, stand-alone reports and corporate homepages of a sample of 116 oil and gas companies in 19 developing countries. The results of this study reveal that the quality of the environmental disclosure of the sample companies is relatively high compared to previous studies. This study has important implications in enhancing the understanding of environmental disclosure practices of oil and gas companies in developing countries.