Bus/train between St. Andrews-Oban and between Oban-Inverness

St Andrews to Oban- 0900 bus 99 to Leuchars Station, 0938 train to Haymarket arrive 1055, depart 1104 Glasgow Queen Street arrive 1148, depart 1220, Oban arrive 1541.
There is also an afternoon train, arriving Oban at 2130.
There is also a coach/bus #X24 at 0840 direct from St Andrews to Glasgow Buchanan Bus Station at 0840, arrive 1130 then the train above.
Also a City link coach from Buchanan, #975, at 1230, arrive Oban 1529.

Oban to Inverness- Oban depart 1211 by train, change at Crianlarich, arrive Fort William at 1609, Fort William depart 1750 on bus #919, Inverness arrive 1952.

Or Citylink to Glasgow at 0745, arrive 1043, or 1255 arrive 1559.
Then City link #M10 depart 1055 Inverness arrive 1433, and hourly thereafter.

Direct trains depart Glasgow Queen Street at 1111, arrive 1429, at 1438 and a change at Perth train at 1645, arrive 2009.

So both journeys are possible.

Thanks for your detailed reply. It helped us get a reality check and change our plans.

Happy travels,
sgh

Be aware, too, that a taxi from St. Andrews to Leuchars won't cost you much. The bus station in St. Andrews I found somewhat difficult to use. Maybe just me.

The bus station in St. Andrews I found somewhat difficult to use. Maybe just me.

Yes, that can only come from someone unfamiliar with using transit. There are only a handful of bus stands- each of which is dedicated to a specific service/destination.
At the far end of the station (at the former ticket/inspectors window) there is a plan of the station, detailing which services leave from which stance. And at each stance there is a board listing departures as well, also real time monitoring screens above each stance.
It is hard to know what else could be done to make it any easier.
Oh and the Stagecoach app also tells you which stance for which service.
The worst you can say about the station is that it struggles with the tourist crowds at a few peak times, being on what is a small site but a larger central site in this small city doesn't really exist. I have encountered the peak evening boarding lines (especially for the X routes) merging with each other. Usually because of tourists who don't understand the concept of waiting in a line.

Yes, that can only come from someone unfamiliar with using transit.

Not "only unfamiliar." I've used lots of trams, buses and light rail, including in countries where I have none of the local language (Belgium, Poland, Czechia and Sweden.) Nowhere else was I as uncomfortable with knowing what was going on as in the St. Andrews bus station.