In order to develop suitable pedagogical methods for inquiry based learning we need an increased understanding of factors that influence students’ work in inquiry assignments. The aim of this study was to investigate how high school students’ ways to work in a collaborative source-based writing assignment was influenced by their individual approach to studying and the teacher’s instructions and guidance in the class. The respondents were 53 high school students who filled out a questionnaire regarding their work on the source based assignment and the OPPI test of their approaches to studying. A factor analysis revealed three work patterns: a collaborative, a labor intense and a subject oriented. The results showed that the collaborative pattern was related to instructional differences, while a subject oriented work pattern was typical for students with a deep approach regardless of instruction. Instructional differences and study approaches also influenced degree of challenges in the project and, to a certain extent, learning experiences. The findings show a complex interplay between personal preferences and instructional interventions in forming students’ paths through source based writing assignments.