This quasi-experimental study uses a pre-/post-intervention approach to investigate the quality of undergraduate students' arguments in the context of socioscientific issues (SSI) based on experiencing a semester of traditional "cookbook" instruction (N?=?79) or a semester of argument-based instruction (N?=?73) in the context of an undergraduate science laboratory course. Findings from this study indicate that the students experiencing the argument-based instruction generated significantly better arguments than students in the traditional course after the intervention. Specifically, the students in the treatment group were better able to include rationales in their arguments supporting their stance on the SSI task. Implications for instruction in undergraduate science laboratory courses, including the use of scientific argumentation as a means of enhancing science proficiency and science literacy, are discussed.