In this study of her university teaching practice in science education, an action researcher sought the collaboration of a colleague to address research design issues related to researcher bias. The colleague worked in another field of study (mathematics education) but was experienced in qualitative research, notably interviewing. Acting as an outside interviewer, the colleague used her skills related to the dynamics of interviewing and her knowledge of the content of the study to elicit pertinent information from interviewees about the effectiveness of the first author's teaching. The additional expertise enhanced the quality of the study considerably and highlighted how "two heads can work better than one". In the process both researchers gained appreciable professional knowledge from each other. The first author gained a greater understanding of the interview process while the second author acquired an appreciation of how pedagogical content knowledge (PCK) is viewed within the context of science, raising the possibility that there are some differences in the way that PCK is conceived within science versus mathematics. The collaboration also raised some unforseen issues that may have impacted on the nature of the findings. This paper discusses the positive outcomes of using a colleague as an interviewer in an action research project as well as some of the pitfalls that can also accompany such teamwork. Consideration is given to the issue of balancing the costs and benefits of this approach to data gathering.