We will need to get to Oslo from Stavanger on July 18th. I was thinking flight to save time, but considering train travel too. It is my husband and myself. Any thoughts/suggestions you can give us? Thank you!
Most practical is train.
https://www.vy.no/en
If you want to travel as a tourist a rental car is very meaningful because very scenic drives if you do not take the shortest / fastest way but something like E 134.
Do not use the link the post above, trains to/from Stavanger are not operated by Vy. Use https://go-aheadnordic.no or www.entur.no instead.
Apart from that, yes take the train. It is a very scenic trip. If saving time is more important, take the overnight train. Driving is also an option, but in that case I recommend that you spend a night somewhere along the way.