Accurately documenting the occupational biographies of older people can be challenging given their lengthy duration and the complexity of contemporary employment. This paper shows how a traditionally quantitative occupational history calendar (OHC) instrument can be adapted for use in a mixed methods research design, to gather in-depth information about long working lives. The OHCs were embedded within semi-structured interviews and recorded lifetime work histories of between 33 and 53 years for 56 participants. Sequence analysis of the calendar data was undertaken in parallel to thematic analysis of interview transcripts. This included in-depth exploration of the factors motivating occupational changes and transitions and their impact in older age. Mixing methods allowed us to collate data over relatively long periods of time and enabled an examination of the complex interplay between work, family and personal circumstances that shapes employment histories. Selected research findings are used to demonstrate how this tool can effectively facilitate the exploration of long working lives.