We conduct a series of laboratory experiments to study how groups aggregate information in settings in which group members repeatedly observe both private information about the state and either others members' actions or their actions and signals. Group members share common interests in guessing the state. In addition to varying the information structure, we also vary the group size and study whether large groups are better at aggregating information than smaller groups. The results of the experiments show that large groups do better than small groups when group members observe each other's private information in addition to each other's actions. However, when only the actions of peers are public, large groups fail to perform better than smaller ones. We explore the underlying mechanism behind these aggregate patterns and identify how individual beliefs respond to different pieces of information available to our participants.