Driving from Oban to Edinburgh- how to make a day of it?

St. Conan's Kirk, at the north end of Loch Awe.

Will you have been to Stirling Castle yet? That was our favourite site in Scotland.

Kilchurn Castle at the top of Loch Awe is always worth a stop. Then you can decide if you want to go down to Inveraray and along the A83 or carry on the A85 and A82 and A84. For the latter I would always stop at Callander, and in particular Stirling for the castle, Bannockburn and Wallace Monument.

There are a few route options and any will offer you plenty of stops.

There are so many different options, it is difficult to know where to begin ...

Option 1

Take the A85 from Oban through Crianlarich towards Lochearnhead. (Kilchurn Castle suggested in a previous post is currently closed for conservation works, although the outside can be seen...) Think about the short detour along the A827 to Killin and the Falls of Dochart. Back on the A85 to Lochearnhead, take the A84 head towards Callendar (coffee break and explore.) Think about doing a detour on A821 to Loch Katrine and go for a 45 minute cruise on the loch. continue on A821 to Aberfoyle for lunch. There are a couple of easy walks you could do from here:

https://www.walkhighlands.co.uk/lochlomond/lochan-spling.shtml

https://www.walkhighlands.co.uk/lochlomond/doon-hill.shtml

Continue on A81 and A 873 and consider a slight detour to Doune for Doune Castle and/or Dunblane Cathedral.
You can then pick up the M9 (busy) past Stirling for Edinburgh or alternatively take the A9 and A907 which takes you along the north side of the Firth of Forth through Clackmannan where you pick up A977 and then A985 for Culross. Depending on time, the palace may be closed for the day but this is still and interesting place to walk around. It was used for many scenes in Outlander. Later in the afternoon the worst of the visitors should have left! Cross the Forth Road Bridge for Edinburgh.

Option 2

Stay on the A85 from Lochearnhead through Comrie an attractive small village and a possible coffee stop. Have a look at this short walk or there is this one.
Crieff, larger but equally attractive is a good place for lunch. Drummond Castle Gardens off the A822 are one of the best formal gardens in Scotland. The view from the top of the terrace is jaw dropping. (The castle isn't open and there isn't a cafe). Allow plenty of time to walk and enjoy.

Back on A823 continue through Gleneagles (of golfing fame) to the wonderfully named Yetts o'Muchart to Dunfermline with its Abbey where many Scotiish Kings were buried, including Robert the Bruce. The ruined abbey is in the care of Historic Environment Scotland and entereed separately.

From Dunfermline head to Edinburgh over the Forth Bridge.

Wow thank you so much for taking the time to respond! Such great suggestions!

Now to throw in a curve ball, Cruachan power station, just off the the A85 outside Oban. By power station, it is a hydro electric plant in a hollowed out hill. I keep meaning to visit myself.

Cruachan is not the famous one that is there so people can make tea. That IIRC is in Wales.