Liz Truss, who was formerly Justice Secretary, has been moved to the role of Chief Secretary to the Treasury "attending Cabinet".
It will be seen as a demotion from her former position.
Theresa May is expected to receive a frosty reception when she meets the 1922 Committee later. But what do we know about the group?
The Prime Minister appointed her former leadership rival as Environment Secretary as she confirms her new top team.
He insisted he would be backing Theresa May as leader and has warned MPs to "calm down and get behind the Prime Minister".