I seem to have found a way to do this:
The only caveat seems to be that all of the Vendors on the Item Receipts need to be the same.
1. Click on Enter Bills from the Home Screen -> Select the Vendor.
2. This should open a dialogue box about Open Purchase Orders -> Select Yes
3. Select all POs that need to be on the Bill -> Ok
For me this combined all of the POs selected and created one Bill.
For reference, I use QB Enterprise Desktop.
Hope this helps!
