Abstract: A preassembled and prewired crossarm assembly of high intensity discharge luminaries mountable on a light pole. The assembly includes an elongate, tubular bar that is supported on a ballast-receiving box attachable to the light pole so that the weight of the ballast box is centered on the pole. Members are employed for adjustably mounting the luminaries from the tubular bar in a spaced apart relation. Each mounting member has a wire-receiving passage means in communication with the interior of the tubular bar and an associated luminary, and aligned openings are formed in the bar and the ballast box for the disposition of electrically conductive wiring that connects the luminaries to the ballasts.