Our collaborative action research addresses a challenge in initial teacher education pertaining to the lack of theoretical coherence between teacher candidates' understandings of teaching and learning. The group comprised of three science teacher candidates (Authors 2 and 3) and a university faculty member (Author 1). Through a loosely adapted learning study approach, we embarked on the process of learning to apply a theoretical lens, i.e. variation theory, to frame lessons taught during the school-based practicum; we focused on the use of variation, which is a pedagogical strategy that is undertheorized in biology education. In this paper, we provided a description and reflection of the theory-framed lessons teacher candidates in our group taught. Data sources included lesson plans and materials, video recordings of lessons, reflections and teacher interviews that promoted further articulation of our experiences of the action research process. By comparing our employment of variation theory to frame lesson planning, classroom teaching and student learning, patterns of variation were reflected upon and theorized through the group process. This expanded our collective understandings about the application of variation theory to biology teaching. The paper thus demonstrates the theoretical work we engaged in as an ongoing and dialectical exploration of practice and theory.