During WW1 Major Wray served on the Western Front with 2nd Battalion, Otago Regiment, NZEF, and was awarded the Military Cross for his role in In the attack on the Switch Line, south-east of High Wood, on 15th September 1916.

Military Cross (MC) citation : L.G. 1 January 1917, p46, Rec no 383 : Captain (Temp Major) William George Wray, 2nd Battalion, Otago Regiment, NZEF, WW1

"In the attack on the Switch Line, South-east of High Wood, on 15th September 1916. This officer, though wounded in the hand during the advance, refused to go to the dressing station and preferred to remain with his battalion as so many of his brother officers had fallen. He remained and sited the New Switch Line and helped to consolidate it for eighteen hours until relieved by another battalion. His example had a most inspiring effect on the men who continued the consolidation all day under heavy fire."