The aim of this study was to investigate the kinds of argumentation schemes generated by pre-service elementary science teachers (PSTs) as they perform inquiry-oriented laboratory tasks, and to explore how argumentation schemes vary by task as well as by experimentation and discussion sessions. The model of argumentative and scientific inquiry was used as a design framework in the present study. According to the model, the inquiry of scientific topics was employed by groups of participants through experimentation and critical discussion sessions. The participants of the study were 35 PSTs, who teach middle school science to sixth through eighth grade students after graduation. The data were collected through video- and audio-recordings of the discussions made by PSTs in six inquiry-oriented laboratory sessions. For the analysis of data, pre-determined argumentation schemes by Walton were employed. The results illustrated that PSTs applied varied premises rather than only observations or reliable sources to ground their claims or to argue for a case or an action. It is also worthy of notice that the construction and evaluation of scientific knowledge claims resulted in different numbers and kinds of arguments. Results of this study suggest that designing inquiry-oriented laboratory environments, which are enriched with critical discussion, provides discourse opportunities that can support argumentation. Moreover, PSTs can be encouraged to support and promote argumentation in their future science classrooms if they engage in argumentation integrated instructional strategies.