Abstract
This study aims at examining the use of authentic materials emphasizing more on the 21st century learning methods, namely 4C: communication, collaboration, critical thinking, and creativity in an advanced grammar class. This is an action research as an effort to increase students' ability. Initial data were obtained from a pre-test. The participants in this study were 51 students of an English Education department. Then, in the teaching and learning processes, authentic materials were used in 4C formatted principles. Initially, the study was offline but forced to go online, due to the Covid-19 pandemic, and the treatment with authentic material was provided with the help of the Google classroom and Google Meet application systems. Data were qualitatively and quantitatively analysed. Qualitative analysis was conducted to observation data, while quantitative analysis was carried out to test scores. The study found that (a) the students tend to be more interested in learning dealing with the authentic material although they found it more difficult than dealing with non-authentic material; (b) students seem to enjoy the learning process as the authentic material are up to date (the content of the information in the texts). Comparing the pre-test and post-test results, the study concludes that the application of the 4C learning method with authentic materials in advanced grammar courses can significantly improve students' grammar ability.