The 1st Battalion sailed on the Gaika on 22nd December 1899, and arrived at Cape Town on 13th January 1900. Along with the 2nd East Kent, 2nd Gloucesters, and 1st West Riding Regiment, they formed the 13th Brigade under Major General C E Knox, and part of the VIth Division under Lieutenant General Kelly-Kenny. The doings of the division and of the brigade are sketched under the East Kent Regiment.
The Oxfordshire Light Infantry had, along with the Buffs and Gloucesters, sharp fighting with Cronje's rear-guard on 16th February 1900. The enemy were found to be occupying a large kopje on the right bank of the Modder for the purpose of covering the retreat of their main body and convoy. With difficulty the Oxford Light Infantry got across and then advanced to the attack of the position. Several companies got within 200 yards of the enemy, while the West Riding Regiment endeavoured to turn the enemy's flank, but the Boers held on stubbornly till darkness. The Oxford Light Infantry lost 10 killed and about 40 wounded, and in the encircling battle of the 18th at Paardeberg they were very heavily engaged, as were practically the whole of the Vlth and IXth Divisions. The Oxfords lost 2 officers killed, 3 wounded, and about 5 men killed and 30 wounded. Four officers of the battalion were mentioned in Lord Roberts' despatch of 31st March 1900.
After Paardeberg the battalion was never very desperately engaged, although they took part in a great deal of fighting and endless marching.
In the beginning of June the battalion moved up to Kroonstad and garrisoned various posts on the lines of communication.
For a period of about four months, commencing the end of July 1900, they, along with the 3rd Royal Scots, 17th Battery RFA, and some mounted troops, formed a column under Major General C E Knox which tramped about on both sides of the railway between Kroonstad and the Vaal, sometimes pursuing Boers and at other times clearing them from the neighbourhood of the line. It will be remembered that De Wet, having broken out of the Brandwater basin in July, was occupying the Reitzburg hills, south of the Vaal, about the end of that month. In the beginning of August Lord Kitchener assumed command of the different columns encircling De Wet. On the 7th De Wet crossed the river. Knox's force remained on the south side to watch the drifts, and they then operated from Kroonstad to Heilbron and Frankfort, and thereafter on the west of the railway.
On 25th October Barton engaged and thoroughly defeated the Boers under De Wet at Frederickstad, driving them towards the Vaal. Knox, who now had the mounted troops of Le Gallais and De Lisle under his command, engaged them near Rensburg Drift on the 27th October and inflicted severe loss, killing 7 and capturing 9 prisoners, 2 guns, 3 waggons; another waggon of ammunition being blown up by a shell from U Battery.
On 3rd November Le Gallais found the Boers in force near Bothaville, and following them up, he surprised them on the night of the 5th, and had five hours' heavy fighting before he was reinforced by Knox with De Lisle's Mounted Infantry. "The enemy were completely defeated. This was a most successful engagement, reflecting great credit on Major General C Knox and all serving with him". The captures included 6 guns, "1 pom-pom, 1 maxim. All the enemy's ammunition and waggons and 100 prisoners were taken, and 25 dead and 30 wounded Boers were left on the field ... Our casualties were 3 officers and 7 men killed, 7 officers and 27 men wounded". Le Gallais, "a most gallant and capable leader", was among the killed. In his official report of the action, Major Taylor, U Battery, said that about 5 am Major Lean with the 5th Mounted Infantry captured a Boer picquet, galloped on and found a Boer laager in a hollow. His men at once opened a heavy fire. Ross's 8th Mounted Infantry came up on the left, and the 17th (Ayrshire) and 18th (Glasgow) Imperial Yeomanry took and held positions on the right. The Boers fought hard, but the 7th Mounted Infantry and afterwards De Lisle's Colonials came up, and at 10.15 am the remaining Boers surrendered. The 5th (Warwickshire) Imperial Yeomanry were also mentioned by the Press Association correspondent as being present. The Mounted Infantry, including the men of this battalion, were specially praised by Major Taylor.
In Lord Roberts' final despatch 9 officers and 18 non-commissioned officers and men of the Oxfordshire Light Infantry were mentioned.
Shortly after the fight at Bothaville General Knox was ordered to the south-east of the Orange River Colony, and on his departure complimented very highly the infantry battalions who had trudged with him so long. During the remainder of the campaign the battalion was generally on garrison, but frequently a portion was out on column work. During the first six months of 1901 the battalion was the garrison of Heilbron, from which they marched to Kroonstad and thereafter entrained for Bloemfontein. In September the Oxfordshire Light Infantry were, along with the 2nd Scots Guards, erecting blockhouses between Kopjes Station and Potchefstroom, and thereafter the battalion was part of the garrison of the line. For a great part of 1901 about 120 men of the battalion were with the column of Colonel Western, which operated in the Western Transvaal, the Orange River Colony, and also for a time in Cape Colony.
The Mounted Infantry of the Oxfordshire Light Infantry were with General Clements in the Colesberg district, took part in his march to Bloemfontein and in Lord Roberts' advance to Pretoria. At the end of July 1900 they were brought back to the Orange River Colony and did excellent work, being prominent at Bothaville as already stated.
During the latter phases of the war 7 non-commissioned ofiicers and men of the battalion were mentioned in despatches by Lord Kitchener for good work, and in his final despatch 5 officers and 4 non-commissioned officers were mentioned.