On the 14th September the battalion relieved the 2nd Bn Irish Guards in the trenches near Ginchy in preparation for the start of the Battle of Flers Courcelette the following day.

On 15th September, 1916, a full scale attack on the German third line of defences was launched along a front that stretched from Combles through the village of Flers and on to Courcelette and with the three Coldstream Regiments attacking line abreast for the first time. Gabriels 1st Battalion attacked through the middle of line with the 3d Bn on their left and 2nd Bn on their right line and captured their first objective at the Green Line. The villages of Flers, Martinpuich and Courcelette were quickly captured and the enemy was finally pushed out of High Wood, but the breakthrough was not achieved and the reality was that when the battle ended on 22nd September, the front line had just been moved forward a mile or so. The battle is notable for being the first time that tanks were used.