The present invention is a method and apparatus for forming the upper portion of a drilled concrete pier that utilizes a flexible cylindrical form and a removable cage frame to stabilize the form during the pouring of concrete into the form. The cage frame comprises a circular ring having a space-forming split therein and a plurality of rigid leg rods each having proximal and distal ends, where the proximal ends of the rods are attached to the circular ring at circumferentially spaced apart points and the rods depend from the ring in mutually parallel relation. The legs of the cage frame are inserted into the cylindrical form prior to the concrete pour and removed immediately after the pour.