I know that the CC teaches that all Catholics are obligated to attend Mass on Sunday or Saturday evening if it is reasonably possible. This question is not about what conditions make it reasonable and non-sinful to miss Mass. When a priest (or a bishop) says/performs/celebrates Mass on Sunday or Saturday evening, does that count for him as fulfilling his Sunday obligation, or does he have to additionally attend and sit in the pews during another priest’s Mass? I guess the same question can be applied to deacons and other people with specific roles in the Mass - do they fulfill their Sunday obligation by being at a mass where they fulfill those roles during the service or do they have to go back and see it again “from the pews” as an regular worshiper?
Priests fulfill their obligation by celebrating Mass.
all Catholics are obligated to attend Mass on Sunday or Saturday evening if it is reasonably possible.The norms permitting the celebration of Sunday Mass on a Saturday evening are not overly detailed and thus different practices and notions have arisen around the world.
Even though this practice is relatively recent with respect to the Sunday Mass, the Church had long maintained the custom of beginning the celebration of important feasts the evening before, with first vespers. This was inspired by the concept of a day in the ancient world which divided our 24 hours into four nocturnal vigils and four daylight hours, the day commencing at first vigil.
benefaciat vobis Deus et vos custodiam: signofcross::
But the point of the OP was whether celebrating the Mass - as the priest does - “counts” as ATTENDING Mass, not whether vigil Masses are legitimate. And of course priests and deacons most certainly do fulfill the obligation in the setting of their saying / assisting at Mass.
Really, a priest’s obligation is fulfilled even if he sits in choir.