Oza dos Ríos houses rests of different times that make demonstrable its origins with vestiges even from the time of the castors (stone fortifications). From that time we conserve a huge amount of undertaker constructions, most of them in high parts of the mountain, in the Monte do Gato. These places were retaken in roman time where agrarian and miner economy where complemented. A good example of what we have just said is the undertaker wake of Mazarelas (today at he archaeological museum of San Antón – A Coruña).

 During the Middle Ages, the number of assents increases and get farther from high, fortified land tops, so that agricultural activities can be better looked after. This period is leaded by Religious Orders, such as Saint Martin's and Saint Benito's. The Feudal System was was controlled by Monasteries, an example of which would be the Monastery of Cines (with its original church from the 9th century) and another one that is supposed to be located in San Pedro de Oza’s church on 1155. Also, other medieval constructions are important like: the bridge located Sta. Cruz de Mondoi (that we share wiht Betanzox) and the temples of Santa Cruz de Mondoi, Santa Mª de Cuiña (which houses interesting mural pictures from the 15th century), Santo Tomé de Salto, San Martín de Bandoxa (that dates back from the time of Bernardo II : 982-999), Santiago de Reboredo, San Pedro de Oza, San Pedro de Porzomillos and probable, San Estevan de Vivente where were found inscriptions from the same centuries.

In the Low Middle Ages, the existing parishes were Betanzos, Parada, Oza and Fervenzas, all of them within the Province of Betanzos.

 The project conceived to put into practice the July 23rd , 1835 Royal Decree was definitely approved on the 6th of June, 1836. At that time, the project for the Judicial Party of Betanzos suffered some modifications; Regarding the Council of Oza, an agreement was reached that a new parish would be joined to it. This parish was San Nicolás de Cines, which had so far been part of the Abegondo Council Project.

On June 18th 1836 the final placement for the Judicial Party of Betanzos is published. According to it, the Council of Oza includes the following parishes: San Pedro de Oza, San Esteban de Parada, San Martín de Bandoxa, Santiago de Reboredo, Santa María da Regueira, San Pedro de Porzomillos, Santa Cruz de Mondoy, Santo Tomé de Salto, Santa María de Cuíña, San Esteban de Vivente and San Nicolás de Cines.

The same month, 27th , S María de Rodeiro was separated from Aranga and joined the Council of Oza.
According to the March 24th 1945 Law, Oza is provided with a Regional Court. The Cesuras Court of Trust is subordinate to it .

Its parishes are subordinate to the Dioceses of Santiago. It was at first called Council of Oza and was later renamed as "Oza dos Ríos" to prevent it from being mistaken for another Council also called Oza.

Sus parroquias dependen de la diócesis de Santiago. En principio se llamó Ayuntamiento de Oza (1836) y posteriormente para no confundirlo con otro Oza, paso a ser Oza dos Ríos (1916).