Current literature points to the importance and benefits of extensive reading. Extensive reading provides contextualized clues for better reading comprehension (Krashen, 1982), and substantial linguistic input (Bell, 1998) needed for language development. Several studies have found a correlation between extensive reading and specific linguistic skills including breadth of reading choices, improved writing skills, ease in oral communication, and improvement in other aspects of language. Literature already incorporates much simplified reading material that would encourage even beginners to engage in extensive reading; however, there has been insufficient research to explore the effects of extensive reading that utilizes authentic materials. Krashen (2011) specifies a crucial need for continuous research in this area in support of the inclusion of extensive reading in the EFL curriculum. Thus, this researcher attempted to add to the literature by investigating the impact of authentic materials as the main source of extensive reading. This quantitative study employed a pre- and post-test design using a simulated English proficiency test and an attitudinal survey. Other data such as course exams and students' class participation records were also included to increase validity. This study intended to discover the effects of extensive reading using online materials on students' language proficiency, and students' attitudes toward the extensive reading activity. The study results indicated a strong relationship between extensive reading and vocabulary development. Students thought that extensive reading also enhanced their overall English ability and knowledge.