This study seeks to develop and evaluate a modified lab inquiry approach to teaching about nature of science (NOS) to secondary students. Different from the extended, open-ended inquiry, this approach makes use of shorter lab inquiry activities in which one or several specific NOS aspects are manipulated deliberately so that students are compelled to experience and then reflect on these NOS aspects. In this study, to let students experience theory-laden observation, they were provided with different "theories" in order to bias their observations in the lab inquiry. Then, in the post-lab discussion, the teacher guided students to reflect on their own experience and explicitly taught about theory-ladenness. This study employs a quasi-experimental pretest-posttest design using the historical approach as the control group. The results show that the manipulated lab inquiry approach was much more effective than the historical approach in fostering students' theory-laden views, and it was even more effective when the two approaches were combined. Besides, the study also sought to examine the practical epistemological beliefs of students concerning theory-ladenness, but limited evidence could be found.