Lunch at Zurich airport or Zurich station on way to Lauterbrunnen?

Murren is phenomenal. I'd say get to Murren for dinner.

There is everything to gain by getting to Murren as quickly as possible because it's such an incredibly stunning place...imo

There are lots of restaurants in the airport as well as the main station. I would probably be tempted to just grab something for breakfast take away at the airport and hop on the train and have breakfast while I sit and watch the scenery go by.

Is it ok to eat food on the train? I'm asking because in Japan, which I frequently visit, it's not done.

It is OK to have a picnic on Swiss trains as long as you are neat about it. Lots of people do this.

There is a grocery store in the Zurich train station with a large “grab and go” section of hot and cold items, including salads. I think it is a Coop but do not recall for sure. It was on a lower level, not the street level. Maybe I can find a map of the station. . . . Or someone else will.

Then there would be no need to store luggage, and you could be on your way to Mürren, arriving in plenty of time to explore and enjoy the views.

Lola, it sounds like there are plenty of places to get food at the airport. The only reason for us to visit the Zurich train station would be if there isn't a variety of food available at the airport.

Andy,

The method I'd use in that situation is to pick up a sandwich and a soft drink at one of the many stands in the rail station, and then have lunch on the train. That way you won't delay your trip to Lauterbrunnen and you won't have to be concerned with luggage storage. I can't remember what food stands operate at Zürich airport but there are lots of them at Zürich Hbf. There will likely be a restaurant car on the train as well.

I'd suggest stopping at an ATM at the airport to get some Swiss Francs before you get to the train, as you'll definitely need them. For example, Swiss rail stations have pay-per-use McClean washrooms facilities, and I've found that they don't accept Euro. You'll likely be transiting through Basel SBB and that's the case there. If you want a coffee after lunch, there will likely be an employee with a cart working the train, so you'll need money for that too (they usually accept Euro).

As others have mentioned, I'd also recommend getting to the Berner Oberland as soon as possible so that you can do a walkabout and enjoy a nice dinner before it gets dark.

If you don't stop for anything yet, I'd guess that somewhere around 2pm you'll be arriving at Interlaken Ost. It takes about 3 hrs from Zurich to Interlaken Ost.

Trains to Lauterbrunnen leave every half hour from there. Since there is a HUGE Coop store across the street from the station at Interlaken Ost, you could grab ready to eat food or other supplies there for a half hour. That store has everything from all foods to clothes to hardware to Swiss chocolate candy bars.

Eating lunch on the train is normal in Switzerland and every other European country I have travelled in. Just remember to take your rubbish with you and don't leave a mess.
I too would recommend getting a train straight from the airport to Lauterbrunnen. But I can't remember what food is available between Arrivals and the station platforms, I am usually too busy heading for my train.

I remember there being lots of different kinds of food stalls in the Zurich airport transportation center, near the SBB ticket center. Eat it on the train. Each row of seats on the train has a little table and garbage bin for that purpose.

There are several Coop like shops with premade sandwiches in Zurich that we have used before. We have stopped in Interlaken Ost and bought supplies for our stay in the Lauterbrunnen Valley.

There is a good food court at the airport, so it would be much handier to eat there rather than roam around Zurich HB looking for somewhere to eat. The big supermarkets are also there and offer plenty of options to pick up something to eat on the train. It it were me I would pick up some stuff at the supermarket in the airport and picnic on the train.

Here is a link to what is at the airport,

https://www.zurich-airport.com/passengers-and-visitors/shopping-and-attractions/storefinder-en#q=cat:23

I also would not waste time going into Zurich. There are Coop and Migros stores as well as many other food options at the airport.

And don't forget your bottle of wine or beer to take with you on the train! Yes, eating on the train is perfectly normal. There are also garbage receptacles on the train.