In many countries, especially in Asia, the group package tour (GPT) is the mainstream mode of outbound travel. Nevertheless, surprisingly little effort has been devoted to improving our understanding of the grounded service features of the GPT. In order to fill this gap and thereby enhance the foundations of group travel theory, this study conducted exploratory research to identify the critical service features of the GPT. Sample data come from the customer lists offered by a large wholesale travel agency. Data were collected from both customers and employees using critical incident technique (CIT). After the data collection, a rigorous categorization exercise was conducted; 25 distinct grounded service features emerged from the data. At the end, the authors also discuss implications for future systematic investigation, model development, and make recommendations for tour operators.