The 157th (Simcoe Foresters) Battalion, CEF was a unit in the Canadian Expeditionary Force during the First World War. On 30 November 1915, the 35th Simcoe Foresters was authorized to raise the 157th Battalion. Under the command of Lieutenant-Colonel D.H. MacLaren, the 157th was tasked with constructing a new army training camp on the Simcoe Pines Plain, which was to be named Camp Borden. Construction began in May 1916 with the companies from Barrie and Collingwood. A second company from Barrie arrived in June to help speed-up the construction. As such, the 157th became the founding battalion of Camp Borden, which it constructed to accommodate 40 infantry battalions in 10 brigades. Before the Camp was opened the remainder of the 157th and the entire 177th Battalion (Simcoe Foresters), CEF under the command of Lieutenant-Colonel J.B. McPhee, arrived. By that summer, Camp Borden was home to 36 CEF battalions in 9 brigades before they embarked overseas
Based in Barrie, Ontario, the unit began recruiting in late 1915 in Simcoe County. After sailing to England in October 1916, the battalion was absorbed into the 1st, 19th, 116th, and 125th Battalions, CEF, and the 8th Reserve Battalion. The Battalion received its Regimental colours on 12 October 1916 at Camp Borden, which were subsequently laid-up in St. Andrews Presbyterian Church, Barrie, Ontario on 10 October 1919. The Colours were reclaimed by The Grey and Simcoe Foresters, which perpetuates the 157th, on 18 June 1982 and deposited in the Regiment's Barrie Officers' Mess.
The battalion had one Officer Commanding: Lieut-Col. D. H. MacLaren.