In this paper, we examine the characteristics of a discourse that show evidences of collective knowledge construction and investigate the impact of task design and facilitation on in situ small group collaborative learning. To examine discourse types, all audio-recorded verbal data of the three groups of secondary students is transcribed, coded and analysed with respect to two key dimensions in the knowledge construction process, namely, the epistemic and the social. Tasks were categorized largely into performative and knowledge-generative. Analysis showed that different epistemic activities and the nature of facilitation have a definitive bearing on group discursive moves and more importantly, the presence of a real world context could generate intense knowledge co-construction even for mundane performative tasks. In conclusion, we propose that a three-prong approach (FAT) -Facilitation, Activities in-situ, and Technology - should be considered to support meaningful collaborative learning practices in mobile learning.