In Horizon 2020, open access to scientific peer-reviewed publications has been anchored as an ‘underlying principle’, making it obligatory for all projects. In addition, as of 2017 H2020 projects are by default part of the Open Research Data Pilot, although it remains possible to opt-out.
General overview: Guidelines for Open Access to publications and data in H2020.
More information on the Open Research Data Pilot: Guidelines on FAIR data management in H2020.
Check what EC policies and mandates are applicable to your organisation or project.