Business process management plays an important role in the management of organizations. More and more organizations describe their operations as business processes. It is common for organizations to have collections of thousands of business processes, but for reasons of confidentiality these collections are often not, or only partially, available to researchers. On the other hand, research on techniques for managing process model collections, such as techniques for process retrieval, requires large collections for evaluation purposes. Therefore, this paper proposes a technique to generate such collections of process models, based on the properties of real-world collections. Where existing techniques focus on the structure of the process models, the technique proposed in this paper also generates task labels that consists of words from real-life task labels and considers semantic information of node and edge types. We evaluate our technique by applying it to generate two synthetic collections of process models of over 60,000 and over 2,000 models, respectively. We show that the generated synthetic collections have similar properties to the original collections. To the best of our knowledge, this is the first technique that can generate synthetic BPMN models, thus enabling experimentation with process collections that have laboratory-set quantitative parameters and qualitative properties that are based on real-world process model collections.