On 25 July 1810, Colville was promoted major-general and at once applied for a command in the Iberian Peninsula. In October 1810 he took over the command of the 1st brigade of the 3rd Division, which was under the command of Thomas Picton. He soon became not only Picton's trusted lieutenant, but one of Wellington's favourite brigadiers. He commanded his brigade in the pursuit after Massena, and in the Battle of Fuentes de Oñoro, shared the superintendence of the trenches with Major-General John Hamilton at the second siege of Badajoz. He also commanded the infantry in the affair at El Bodón on 25 September 1811, and the 4th division in the place of Major-General Cole in the successful siege of Ciudad Rodrigo. He shared the superintendence of the trenches in the third and last siege of Badajoz with Generals Bowes and Kempt (who replaced the wounded Picton), and commanded the 4th division in the storming of the Trinidad bastion, where he was shot through the left thigh and lost a finger of his right hand.