This paper considers the responses of online students to two distinct collaborative small group structures. In one structure the students worked in closed groups, communicating only with one another, while in the other situation, although the students posted messages only to their own ‘backyard’ group they were also able to read the dialogues of all the other groups, ‘over the fence’. Both structures were effective mechanisms for developing group skills of joint inquiry and problem solving tailored to different learning environments, although each had inherent advantages and disadvantages. The closed group structure encouraged sharing, while the ‘over the fence’ approach allowed students to be supported by behaviours and information from the wider class. The structures also encouraged a diagnostic attitude toward the learning process, as group members were able to examine their own experiences in the group and to extend their learning in metacognitive dimensions.