Editing Openai/69186d20-2d14-8013-b9c6-c09000f173f6 (section)

===== Standard-ish pronunciation: =====

: 
* initial o → schwa /ə/ (very reduced, like English a in about).
* ráis → /ɾˠaːʃ/ - á = long /aː/ - s is slender /ʃ/ because of following t(e).
* final te → /tʲə/ (slender t + schwa).

Stress is on the second syllable:

: 

This is one of the standard exceptions to “stress the first syllable” in Irish. Why?
* The first syllable is a weak, reduced vowel before a consonant cluster (just /əɾ-/).
* The second syllable has a heavy nucleus /aː/ plus the consonant cluster /ʃtʲ/.
* In many loans with a weak initial syllable and a heavy following one (especially from French/English), Irish allows non-initial stress; oráiste has become fixed with stress on ráis-.

So your ear is right: it really is second-syllable stress, and Irish speakers treat the initial o- as a kind of unstressed pre-syllable.