The purpose of history education in Austria has changed over at least the last decade. While the focus used to be to give students a master narrative of the national past based on positivist knowledge, the current objective of history education is to foster historical thinking processes that enable students to form transferable skills in the self-reflected handling and creation of history. A key factor in fostering historical thinking is the appropriation of learning tasks. This case study measures the complexity of learning tasks in Austrian history textbooks as one important aspect of their quality. It makes use of three different approaches to complexity to triangulate the notion: general task complexity (GTC), general linguistic complexity (GLC), and domain-specific task complexity (DTC). The question is which findings can be offered by the specific strengths and limitations of the different methodological approaches to give new insights into the study of task complexity in the domain of history education research. By pursuing multidisciplinary approaches in a triangulating way, the case study opens up new prospects for this field. Besides offering new insights on measuring the complexity of learning tasks, the study illustrates the need for further research in this field – not only related to the development of analytical frameworks, but also regarding the notion of complexity in the context of historical learning itself.