Open Government poses broad challenges to contemporary parliaments with its emphasis not just on openness and transparency but also on participation and collaboration. The situational awareness obtained from citizen-sourcing and the advances in information and communications technology are key enablers for effective and efficient Open Government in parliamentary institutions. Citizen-sourcing, on one hand, may help parliaments be more sensible and effective because citizens are able to improve parliaments’ situational awareness and then influence direction and outcomes for policy making process. On the other hand, exploiting the opportunities created by the emerging ICT paradigms allows parliaments to put Open Government into practice in an efficient way. This paper presents a situational awareness process model to support effective decision-making with citizens’ insights. Based on this model, an architecture for situational awareness-based information services is presented. This architecture makes use of the opportunities that cloud computing paradigm, social media applications and semantic enrichment offer to provide an efficient implementation of Open Government in parliaments. A motivating scenario of the proposed architecture is illustrated to show a use case of a situational awareness-based information service, which has the potential to function as a new mechanism of relationship between a parliament and its citizens to enable collective knowledge in order to enhance the passage of a draft bill.