This descriptive contribution presents some data about a type of vowel harmony occurring in the Sardinian variety of Santa Maria Navarrese and Baunei. These two centres are located in the province of Ogliastra/Ogiastra, in the central-eastern part of the island, on the border between Campidanese Sardinian and Logudorese-Nuorese Sardinian. In addition to the largely attested Sardinian right-to-left metaphony, whereby the word-final vowel may affect the realization of preceding vowels, the variety of Santa Maria Navarrese and Baunei also displays a left-to-right vowel harmony that governs the choice of -os/-us as a plural ending. This phenomenon, which was directly observed in Santa Maria and which is attested in writing in Baunei, affects the formation of certain plural nouns and adjectives, as well as the behaviour of the masculine plural accusative clitic. A description of this phenomenon, with some personal considerations, will be provided with the intent that it might be of interest for further research.