Abstract: In an underbalanced or overbalanced completion, the packer that isolates a portion of the wellbore is preferably a composite mechanically set bridge plug. The composite materials are selected to expedite mill out the plug. A coring mill envelopes the plug as it cuts away the grip of the slips. Internal uphole oriented wickers inside the coring mill grab hold of it before the slip grip is lost to capture the plug in the coring mill. The liner string is rotated to operate the mill or alternatively a downhole motor can be used to run the coring mill. After the bridge plug is milled to a release and capture position, the liner string that can be slotted liner or screen or other tubular is advanced into position further down the usually deviated wellbore.