An apparatus and method for completing an interval of a wellbore while drilling comprises a drill string (52) having a drill bit (30) mounted on the lower end thereof. A completion assembly (50) is positioned around a section of the drill string (52) such that when the wellbore (32) is extended by rotating the drill bit (30) and advancing the drill string (52), the completion assembly (50) does not rotate. The advancement of the drill string (52) and rotation of the drill bit (30) is ceased when the completion assembly (50) has reached the desired interval of the wellbore (32). Thereafter, the drill string (52) is disconnected from the drill bit (30) for retrieval to the surface leaving the completion assembly (50) and the drill bit (30) downhole.