The six musical settings of Mestastasio`s La passione di Gesu Cristo Signor Nostro embody the stylistic changes during the eighteenth century. They contain traditional elements such as ouverture/introduction, duo, and chorus as well as progressive elements such as recitative and aria. The main interest of the present study is focused on the latter. The changing process in recitative can be discernable in the number of accompanied recitatives in each setting, which range from none (Caldara) to more than half of all the recitatives. The stylistic change in aria, on the other hand, can be the most easily observed not in the general trend but in the recognition of the specific ways of transformation in each aria. One of the most famous aria texts from Metastasio`s pen, Apostle John`s aria "Dovunque il guardo giro" is, therefore, selected for the present analysis. The range of aria forms is from Caldara`s five-part da capo with trombone obbligato, Jommelli`s da capo al segno, and Naumann`s dal segno to three-part arias by Myslivecek, Salieri, and Paisiello. Despite the three-part scheme, there is a significant difference in each composer`s treatment: Salieri set it in regular three-part ABA` form; Myslivecek did not employ initial ritornello; Paisiello changed the tempo starting from B section. By analysing stylistic changes in Metastasian oratorios, we tried to obtain a more balanced historical viewpoint on eighteenth-century music. The historical relationship between the transformation of da capo aria form and the establishment of the sonata form will be the topic of a subsequent paper.