A method of milling a window through a casing in a primary well bore and drilling a sidetracked well bore into a formation including running a drilling assembly including a body having an axis defined therethrough, a piston that is movable within a cavity formed in the body, a stationary cutting structure coupled to the body, and a movable cutting structure coupled to the body, milling a window through the casing in a first trip into the primary well bore, drilling the sidetracked well bore in the first trip into the primary well bore, applying a differential pressure across the piston, and moving the movable cutting structure from the collapsed position to the expanded position. The movable cutting structure is coupled to the piston and is movable between a collapsed position and an expanded position.