COS4CLOUD (Co-designed citizen observatories for the EOS-Cloud) aims to design, prototyped and implemented services that address the Open Science challenges shared by Citizen observatories of biodiversity, based on the experience of platforms like: Artportalen, Natusfera, iSpot, as well as other environmental quality monitoring platforms like: FreshWater Watch, KdUINO, OdourCollect, iSpex and CanAir.io. The innovative services will be designed, prototyped and implemented for improving the data and information quality using deep machine learning, automatic video recognition, advanced mobile app interfaces, and other cutting-edge technologies, based on data models and data protocols validated by traditional science. The new services will provide mechanisms to ensure the visibility and recognition of data contributors and the tools to improve networking between various stakeholders. Novel innovative digital services will be developed through the integration of CS products, generated by different providers, following open standards to ensure their interoperability, and offered in agile, fit-for-purpose and sustainable site available through EOSC hub, including a discovery service, to both traditional and citizen scientists. The design of new services will be user oriented, engaging a wide range of stakeholders in society, government, industry, academia, agencies, and research to co-design service requirements. As a result, COS4CLOUD will integrate citizen science in the European Open Science Cloud, bringing Citizen Science (CS) projects as a service for the scientific community and society at large.