There will be multiple companies involved (Berner Oberland Bahn, BLS, SBB, SNCF, maybe RENFE) but that's not an issue as they all acknowledge the pass.

First have a look at these links :

https://www.seat61.com/how-to-use-a-eurail-pass.htm

https://www.seat61.com/interrail-and-eurail-reservations.htm

This journey is definitely doable in a day but not as easy as it should be. We very much need a direct train from Geneva to Barcelona... there are so many flights right now while it could be an easy journey. Well, off-topic…

There are 2 ways to reach Barcelona by high-speed trains :

- TGV from Valence TGV (25€)

- AVE from Lyon Part-Dieu (10€)

Unfortunately the AVE from Lyon cannot be booked online (thanks RENFE...). It is possible to do so on the day on the platform for 10€. It works well right now in the off season but I have no idea how it'll look in the summer. I've heard they can sell folding seats or you can go to the bar if needed. 1st class should also have more availability.

July timetables won't be available for 2 weeks. You may check June timetables, they should be pretty similar but don't forget to check closer to travel as the summer is prone to engineering works. Use DB Navigator app or any other reliable planner.

The Lyon option would be the best one timewise and convenience-wise. Grenoble/Valence would be safer.

For example :

- get to Geneva (trains every 30 min)

- TER Geneva - Grenoble 11:59 - 14:02

- TER Grenoble - Valence TGV 14:30 - 15:33 or 15:30 - 16:33

- TGV Valence TGV - Barcelona-Sants 16:57 - 21:27 25€

Thinking about it you could do it this way :

- get to Geneva in time (trains every 30 min)

- TER Geneva - Lyon Part-Dieu 11:29 - 13:26

Go to the AVE platform -> look if you can spot the train whenever you arrive. Speak to staff and ask for passholder reservations.

Buy reservations in advance for the Valence - Barcelona TGV for peace of mind. If you can board the AVE get a refund for them (possible without fees until departure), if not you'll be able to use them and make it to Barcelona that day anyway :

- TER Lyon Part-Dieu - Valence 14:20 - 15:27

- TER Valence - Valence TGV 16:17 - 16:25

- TGV Valence TGV - Barcelona-Sants 16:57 - 21:27

Questions welcome. :)

Thanks appreciate the feedback