In 1817, with the establishment of the Division of Volunteers of the Prince and his being transferred to Brazil to help with the Conquest of Montevideo, he was given the rank of Field Marshal.

He commanded the Campaign of Banda Oriental, distinguishing himself in the Battle of Paço de Arenas in September 1819.

On 5 June 1821, as commander of the soldiers in Rio de Janeiro, he directed the ultimatum to Prince Pedro that he had to swear to uphold the foundations of the Constitution, dismiss the Count of Arcos and nominate a governing junta.

In October he demanded again that Prince Pedro publicly announce his adherence to the decisions of the Cortes gathered in Lisbon.

Jorge de Avilez resigned from the Government of Arms and, fearing an attack by Brazilian troops, he retreated to Praia Grande, in Niterói, which he fortified but was later expelled by the Prince Regent.

Judged, he was dismissed from his rank of Lieutenant-General and condemned to a year of imprisonment in Castelo de Vide.

With the return of Prince Miguel, he asked permission to go to Portalegre, but was arrested again in June 1828 and sent to São Julião da Barra Fortress.

King Pedro IV reconciled with Jorge de Avilez at the end of the civil war, and appointed him to Military Governor of the Court and Province of Extremadura, with the rank of Lieutenant-General.