The patroness of Osasio is the Santissima Trinità, celebrated on the first Sunday after Pentecost; the village holds the Chiesa Santissima Trinità.
Once a year the festival of the Santissima Trinità takes place, when many people of Osasio and from neighbouring villages gather in the square to eat and celebrate together; the festival falls in spring, on the Sunday after Pentecost. The municipality also holds the Cappella della Madonna dei Sette Dolori, the Cappella di San Rocco and the Chiesa dei Battuti o dello Spirito Santo.
