Include components supplied by the supplier in OSP PO

We are using OSP process and some suppliers are adding some components from their stock to the assembly and shipping the finished assembly to us. In such a case, we need to pay the supplier for both - the services rendered by him and for the components added by him to the assembly. Is there any way to include those components in the OSP Purchase Order so that we can pay to the supplier for the components in addition to his service charges?
Thanks,
Saahil