An exemplary piston may include a piston body having radially inner and outer body mating surfaces. The piston may further include a cooling gallery ring cooperating with the piston body to form a continuous upper combustion bowl surface and a cooling gallery. The cooling gallery ring may have radially inner and outer ring mating surfaces abutted along their corresponding radially inner and outer body mating surfaces, such that the cooling gallery is substantially enclosed. The piston body and cooling gallery ring may be joined together along the radially inner and radially outer interface regions to form a generally one-piece piston assembly. The radially outer interface region may be elongated in a direction parallel to the piston axis, e.g., facilitating a laser welding joining process.