The aim of the WINHO indicators project is to describe and enhance the quality of outpatient oncology care in Germany with indicators. This paper deals with the development of a set of evidence- and consensus-based meaningful indicators to assess the quality of outpatient oncology care in Germany. These indicators are intended to be applied in assessments of quality of patient care in oncology practices, in quality reports and in peer-to-peer benchmarking. A set of 272 already existing indicators was identified through internet and literature searches. After redundancy reduction and addition of newly developed indicators for areas of ambulatory oncology care that were not yet covered, a preliminary set of 67 indicators was established. The further development of the indicator set was based on a modified version of the two-step RAND/UCLA expert evaluation method, which has been internationally established for developing quality indicator sets. The indicators were modified after the first round of ratings. After completing and assessing the second round of ratings, a set of 46 homogeneously positively rated quality indicators is now available for outpatient oncology care in Germany.