During his rule, the borders of Béarn were established more definitively; he defeated the viscount of Dax, and took control of Orthez, Pays de Mixe, and Ostabaret by 1105 and gained Montaner through his marriage to Talesa.

[2] Though technically a vassal of the Duchy of Aquitaine, ruled at that time by William IX, Gaston effectively made Béarn an autonomous territory.

He preferred negotiation and dialogue to senseless massacre, and he and Tancred tried to protect some of the Muslims of Jerusalem by sheltering them in the Al-Aqsa Mosque.

Gaston was a pious man, and upon his return to Béarn he oversaw the construction of many churches destined to shelter pilgrims on the route to Santiago de Compostela.

[5] He also came into conflict with some churches, however; he successfully defended his claims to the territories of the abbey of St. Vincent de Lucq and the monastery of St. Mont.