This descriptive study aims to investigate the instructional effectiveness of Open Educational Resources (OER). It was conducted with 1196 university students who were enrolled in a general chemistry course with an experimental laboratory section. These students voluntarily used OER for their lab activities. Data were collected via a printed, 18-question survey. Results showed that about half of the students were aware of the OER, and half of these informed students used it. Nonetheless, four advantages of the OER were determined: preparation for topic in advance, facilitating learning, time saving, and improving grades.