The RCOC, created in July 1903, was responsible for procurement by contract and local purchase, receipt, inspection and warehousing of stores, accounting, issue and return, if applicable, for all ordnance stores and equipment including ammunition inspection and storage.

The RCASC was added to the permanent Force in the same year and given responsibility for food, fodder and forage and all aspects of rail and sea transportation plus the transport forward of all supplies to the front line.

When war broke out in 1914, the total numbers in the Ordnance Corps including both permanent and non-permanent branches were about 100 members. By 1918, this had increased to over 1315. This rapid expansion and the numerous wartime tasks associated with it, placed enormous strains upon the Canadian Ordnance Corps. All members of the Corps, both old and new, rose to the challenge and took it in stride.

The first contingent of the Canadian Expeditionary Force (CEF) with its embedded Canadian Ordnance Corps component concentrated at Camp Valcartier and sailed for England in October 1914 as an integral part of 1st Canadian Division, which went to France in February 1915.

By 1918, the Canadian Ordnance Corps were supporting 400,000 men, 150,000 French civilians and 25,000 horses in the European Theatre. Recognition of the Corps' outstanding work during the war came in November 1919 when His Majesty, King George V, awarded the designation "Royal" to both the Canadian Army Service Corps and the Canadian Ordnance Corps.

After the First World War, the task of disposal of the huge surpluses fell to the Royal Canadian Ordnance Corps, a task that took two years to complete. In 1924, the Royal Canadian Ordnance Corps re-examined its operating procedures and developed a standardized way of doing business, a set of procedures that remained in force for 15 years until the onset of the Second World War forced a re-evaluation. In the 1930s, the RCOC undertook to supplying and equipping the numerous unemployment relief camps throughout the country.

Until 1944, the RCOC was responsible for the electrical and mechanical repairs for Army equipment. Thus the spares and the responsibility for installing them were vested in the same organization. With increasing mechanization of the Army during the Second World War, it was decided to transfer the electrical and mechanical repair responsibility and a new Corps, the Royal Canadian Electrical and Mechanical Engineers (RCEME) was created to perform this function.

The Second World War was another period of rapid expansion for the RCOC in terms of personnel and infrastructure. The 1st Infantry Division was quickly mobilized and sailed for Scotland in December 1939. This included elements of the RCOC. As Corps and Army Headquarters were formed, there were corresponding RCOC companies formed as well as Lines of Communications troops.

The first Ordnance unit mobilized during the Second World War was dispatched to England in the autumn of 1939 and units and reinforcements continued to flow overseas in an ever-increasing number throughout the war. In 1941, the RCOC was designated a combatant corps.

The military strength of the Corps reached a wartime peak of 25,000 all ranks. By the end of the war, the RCOC was a huge organization with a string of supply depots (four central ordnance depots and five regional depots) and ammunition depots covering the whole of Canada.

Members of the RCOC served in a wide variety of positions including supply depots, the Canadian Mobile Ammunition Repair Units and the Canadian Forward Ammunition Maintenance Sections. They were also widely employed at Roadhead and Railhead Ordnance companies advising and assisting in the pushing forward of spares parts and ammunition stocks to the front.

Although Ordnance is usually discussed in reference to weapons and ammunition, the RCOC also provided some of the comforts which made life bearable for soldiers in wartime, whether that meant mosquito netting in the Mediterranean theatre or sporting goods like football uniforms and baseball equipment for periods of recreation.

Perhaps the most important such service was rendered by RCOC Mobile Laundry and Bath Units in Italy and Northwest Europe, which offered front line soldiers a hot bath or shower and clean socks, shirts, underwear, and uniforms. Sometimes they could even sleep the night in tents. The importance of something so completely taken for granted today cannot be underestimated in a context where men could go for days on end without even taking their boots off.

At the end of the Second World War, many units and training establishments were disbanded and the RCOC was once again faced with the task of disposing of huge amounts of surplus materiel. Much was sold but a large quantity of equipment and stores were re-conditioned and placed in storage as a reserve.

Unfortunately, peace was not to continue for long. The Korean War began in June 1950. Canada formed 25 Infantry Brigade for service there. The RCOC made a significant contribution to the war effort in Korea with 1069 personnel serving in the theatre. Subsequently, members of the RCOC served with the Army in Europe and in support of UN operations in Egypt, India/Pakistan, the Congo, Cyprus and Indo-China.

In order to improve support, an experimental Service Battalion was formed at Camp Gagetown in 1963. This experiment was successful and all of the Brigade Groups changed to the Service Battalion concept in 1968. This was also the year that integration and unification took effect. As a prelude, the Canadian Forces School of Administration and Logistics (CFSAL) was formed on 1 September 1967. The Canadian Forces Reorganization Act was proclaimed on 1 February 1968.

This also marked the formation of the Logistics Branch, which incorporated the supply, transport and finance services of the RCN, Canadian Army and the RCAF. Although the RCOC no longer formally existed, Corps training continued until 1969 when the Logistics Branch training superseded it. Former members of the Corps continued to wear their RCOC badges with pride until the Logistic Branch badge was issued in 1973/1974.