Despite the importance of dual VET for economic growth and stability, internationally, systems struggle with quality assurance and quality improvement. In recent years, numerous research efforts have been made to identify and describe quality aspects in dual VET, especially with regard to in-company training conditions as perceived by apprentices. This has resulted in an outsized number of test instruments, comprising numerous scales and numerous items. The research presented here aims to assemble and organize all existing survey instruments in the VET context and to develop a comprehensive and validated questionnaire for dual VET that measures workplace characteristics (VET-LQI). For this purpose, 43 test instruments were identified and categorized using a qualitative meta-synthesis, and integrated into a general theoretical framework (Tynjälä 2013). The results of the meta-synthesis reveal diverse content areas as the current foci of VET quality research. The applicability of any existing survey is limited, as the majority of studies either focus on a small range of selected categories and/or do not report the validation results of their scales. Hence, a synthesized item pool was used. Short scales were extracted and tested in seven commercial training occupations in Germany, which covered all identified content areas of VET quality research. On the basis of item and factor analyses, 22 scales (containing 99 items) are identified that, taken together, satisfactorily reflect all common workplace characteristic scales in existent measurement instruments. The resulting instrument provides a broad collection of short scales reflecting the various foci of a longstanding and diverse research tradition, and will allow future researchers to analyze in-company training conditions more comprehensively, given limited opportunities and time resources for testing.