He was consecrated at the Cathedral of Saint Lambert of Liège on 30 May.
The new prince vowed to protect the authority and independence of the territory against the government of the Netherlands, the Abbot of Sint-Truiden and the Abbess-Princess of Munsterbilzen.
The reign of Charles of Oultremont was marked more by his ecclesiastical achievements than his political ones.
He fought against Jansenism, against Febronianism, and against immoral writings which came flooding from France.
He created new charitable institutions and enhanced the level of theological studies.
Politically, he was frequently in dispute with the Austrian Netherlands, who had supported Prince Clemens.
He executed numerous works to improve trade, industry and agriculture, and ordered the paving of roads towards France, other German states and the United Provinces.
Charles of Oultremont also encountered problems with the Teutonic Order, who claimed to be exempt of taxation in virtue of their privileges.
Influenced by his brother, he also raised the quarters of nobility from eight to sixteen to be admitted into the council of the nobility.
This effectively reduced the total number of noble families to around 15.