The exceptional reception of Pietro Metastasio's works during the eighteenth century, all over Europe and in the Iberian Peninsula in particular, is well documented. Due to that unparalleled success, it is possible to ascertain Spain and Portugal's participation in international, contemporary tastes and artistic webs, applicable to both composers and performers. However, this internationalisation needs to be nuanced, as some characteristics of the repertoire specifically written for the Peninsula indicate that their court audiences may have had expectations, both social and strictly musical, different from those of the public in opera theatres elsewhere in the continent. In this light, this article investigates in what ways the style of five composers in the international scene - Perez, Galuppi, Jommelli, Conforto, and Corselli - varied when commissioned to write opera seria for the Iberian courts. The statistical analysis of fifteen settings especially written for the court theatres in Madrid and Lisbon, in comparison to the average data extracted from a corpus of 2,404 arias from 126 versions of a select number of Metastasian librettos, allows us to evaluate some particular usages regarding key, metre, tempo, and treatment of the vocal part. In this manner, through quantitative analysis, this article places eighteenth-century Iberian music production and consumption in the context of European opera seria, while ultimately suggesting that its unique musical characteristics were also partly dependent on local musical customs, gender stereotypes, and personal idiosyncrasies alike.