Autonomous software agents provide a promising solution to the needs of decentralised networked systems, able to adapt their behaviour in a complex and dynamically changing environment. Current agent-oriented software engineering methodologies tend to focus on different levels to realise such a self-adapting behaviour, namely the agent individual level and the global system level. The first requires to design a goal-directed agent behaviour, the second to design agents able to optimize their coordination with other peer agents in the organization, giving rise to system-level adaptation. In this paper we propose to extend a goal-oriented engineering methodology to deal with the modelling of organisations that are able to self-organise in order to reach their goals in a changing environment. To deliver on this aim, we combine Tropos4AS, an extension of TROPOS for adaptive systems, with concepts, guidelines and modelling steps from the ADELFE methodology, which provides a bottom-up approach for engineering collaborative multi-agent societies with an emergent behaviour. The resulting MAS has self-adaptation properties, having agents that are able to change their behaviour according to changes in the environment, and having organisations that adapt themselves to changing needs. The approach is illustrated by modelling a collaborative multi-agent system for conference management.