In this report, we introduce a newly developed task environment for experimental team research: the Planning Task for Teams (PLATT). PLATT is a scenario based, computerized, complex planning task for three-person teams. PLATT has been designed to be able to do experimental laboratory research on complex planning and decision making in teams. In this report, we first formulate a series of requirements a task environment has to meet to be suited for such team research. These are in particular: interdependency among team members, necessity of communication, necessity of information selection, necessity to replan, objectively measurable team performance, experimental control, and extensive logging possibilities. Next, we review the different types of task environments used in team research and test these environments against the requirements set. We then describe PLATT. In PLATT, a team of three persons has to develop a plan on the basis of complex and constantly changing information to evacuate a group of people from a hostile area. The three team members each get their own role assigned with unique expertise and responsibilities. These roles correspond to three important sections in the military: S2 - Intelligence, S3 - Operations, and S4 - Logistics. Driven by a scenario, in real time, messages are sent to the team members, and information is selectively made available to different team members on multiple websites. Team members communicate with each other by e-mail. In addition, they all have access to a digital map of the area in which the evacuation has to take place. All actions team members perform are logged by the server. On the basis of the log file, behavioral process measures concerning communication, information processing and team perspective can be construed. Electronic questionnaires during and after task execution, yield measures for (Shared) Situation Awareness, leadership, cohesion, and satisfaction. The outcome measures can be derived from the detailed planning the team has to deliver in a standardized way. Finally, PLATT is tested against the requirements. The conclusion is justified that PLATT better meets these requirements than the reviewed existing task environments. PLATT seems to be a promising new environment for experimental research on planning and decision making in teams.