European legislation requires that tenders for public contracts where the amounts exceed a certain threshold (according to the type of contract) are published in the Official Journal Supplement (S-Series).
Procurement notices are also published online on the EU Funding & Tenders Portal – the online version of the 'Supplement to the Official Journal' – which can be consulted free of charge.
More information on the EU policy on public procurement can be found on the European Commission's website on public contracts.