Ortisei to Venice

Bus #350 from Ortisei ( St Antonius Platz ) to Bolzano Train station . then train to Venice Santa Lucia via Verona ( one change at Verona )

Bus down to Bolzano, then train. You're very likely to have to change trains in Verona. I see one train a day (departing from Bolzano at 3:31 PM) that goes on to Venice. It's the fastest option (2 hr. 54 min.) since you don't have a layover in Verona, but there are many other departures with a change in Verona and taking less than 3-1/2 hours. The direct train is a EuroCity, and it looks as if it will be cheaper than the other fast options, which involve Freccia trains.

Here's the Trenitalia website: https://www.trenitalia.com/en.html. Choose Bolzano Bozen as your departure point and Venezia S. Lucia as your destination.

I'm nearly certain the Alto Adige/Sud Tirol bus schedules are online, but I don't know exactly where. I bet someone else will be able to provide that link.

Thanks to the bus number provided by Steven, I've found the schedule: Ortisei-Bolzano bus schedule

Here is the bus trans planning site acraven mentioned. https://www.suedtirolmobil.info/en/

Get the Südtirol Mobile app for your phone. Very handy.

Thanks so much!