In this study, we characterized GTAs' teaching practices in algebra-based introductory physics "mini-studios," which combine student-centered recitation and inquiry-based labs. We documented both GTA and student actions using an observation protocol adapted from the Laboratory Observation Protocol for Undergraduate STEM (LOPUS). We observed 72 mini-studio sessions led by 11 GTAs over two semesters. We used an agglomerative hierarchical cluster analysis and identified three clusters that described the similarities and differences between individual sessions. Two clusters contained sessions characterized by more interactive GTAs but they varied in the amount of feedback, lecture and whole class questioning the GTA provided. In the third cluster, GTAs tended to wait for students to call on them before engaging. Student behaviors also varied between the clusters, suggesting correlations between student behaviors and GTA instructional styles, in contrast to previous findings with LOPUS in other contexts. We discuss implications of these findings for future research.