Group work is permitted for the EPQ (see page 7 of the specification) but there are some considerations.
A student must independently choose their own title but can choose to participate in a bigger research project for their EPQ – this must be an individual choice though. The group project must allow students to set their own aims and objectives within the bigger project so they would be able to fulfil the criteria for the EPQ.
They must be given the opportunity to demonstrate the ability to independently plan, research and evaluate in order to fully access the marks available, and each student would need to have a clearly defined role even if they are working towards the same outcome.
If one (or both) of the students is selected for moderation then their individual project should be sent.