A large number of network applications today allow several users to interact together using the many-to-many service mode. In many-to-many communication, also referred to as group communication, a session consists of a group of users (we refer to them as members), where each member transmits its traffic to all other members in the same group. In this paper, we address the problem of designing and provisioning of WDM networks to support many-to-many traffic grooming. Our objective is to minimize the overall network cost, which is dominated by the cost of higher layer electronic ports (i.e., transceivers) and the number of wavelengths used. Based on different WDM node architectures, we propose four different WDM networks for many-to-many traffic grooming. For each network, we analyze the many-to-many traffic grooming problem and provide an optimal as well as a heuristic solution. A comprehensive comparison between the four networks reveals that each of the networks is the most cost-effective choice for a certain range of traffic granularities.