Best time to buy intra-Europe flights? (specifically Barcelona to Geneva or Zurich)

At $74/pp you aren't risking a whole lot if you say have to change your plans and those tickets are non-refundable. If you are confident that your plans are firm (that you really want to fly that day and at that time), I'd book the tickets as soon as easyJet's come out. If prices go down a little, so what? They might go up too. I think the discount airlines do tend to see prices higher the more seats sell on each flight - but it can be a guessing game.

I've never flown Vueling. I have flown easyJet but not in a long time.

What I would remind you to do is research the extra fees you should expect to pay with the budget airlines. They may charge for things like checking bags more than Swiss Air would charge. Some budget airlines even charge you for printing a boarding pass at the airport vs. doing it ahead of time online - so read the rules and restrictions carefully! Don't assume they operate like Delta or Swiss Air. They also tend to be very strict about enforcing weight and size limits on bags that other airlines ignore. It might be that the Swiss Air flights wind up costing about the same or even less after the fees are added - all depends.

Easyjet and most of the other airlines use a price model where the tickets start cheap (advertised as the "from" price) and then go up the nearer it gets to departure date. How fast they go up and to what price, is dependent on how well the tickets sell.
So the principle is always buy as soon as you are prepared to commit to a date.

And don't forget once you buy there are no refunds, changes of date are either not possible or cost.
Baggage costs extra, book that the same time as you buy your tickets, it will cost more at the airport. Makes sure you print out your boarding "card" before you go to the airport (before you leave home). Hand luggage limits are HARD. One item means one item.

Skyscanner is a useful source for European one-way budget flights. It shows three carriers BCN-Zurich: Vueling, Swiss, and Air France. They all operate similar systems -- a low opening fare with add-ons priced separately (fees for advance seat selection, checking a suitcase, and so on.) That information is up-front so the options should be clear. I think you are lucky to have such a choice. The one risk in booking far in advance is that the schedule might change before July. On a simple itinerary, that's less of a problem as some flights are sure to be running.

Another good source is the Wikipedia article about the airport. These always have a list of destinations from that airport: https://en.wikipedia.org/wiki/Barcelona%E2%80%93El_Prat_Airport#Passenger

• Barcelona to Zürich: Swiss and Vueling
• Barcelona to Geneva: Easyjet, Swiss and Vueling
• Barcelona to Basel: Easyjet and Vueling

Depending if you want to spend any time in Switzerland or not, Basel or Geneva may be as convenient as Zürich. Basel and Geneva are both often cheaper than Geneva because they have more cut price airlines than Zürich.

As you are not doing this on a through ticket, you will have to pick up your bags from the first flight first, and check in again in Zürich for your second flight. The will be no immigration when you land as both Spain and Switzerland are in the Schengen Area.
If you are doing both flights on the same day allow plenty of time, if you miss your second flight, you have no fallback, neither airline is responsible.

Thanks, all! We know the exact date that we want to fly from Spain to Switzerland (we'll be finishing up a Mediterranean cruise) so it looks like the best bet is to start staking out the fares tomorrow when easyJet releases! We usually do one bag per person regardless of trip length (do laundry on long trips--in this case, on the cruise ship) and in measuring our bags, it looks like we will be OK on easyJet but not Vueling, so that helps narrow it down a bit.

Just to clarify - it sounds like some of you were saying that we can check in to our intra-Europe flight from the United States and print a boarding pass in the US several days before our flight, correct? I hope that is the case as I don't want to have to print a boarding pass from a cruise ship--sounds expensive!! That is quite different than US airlines. Do budget airlines allow digital boarding passes on smart phones like Delta, etc.?

Also, do budget airlines like easyJet have a provision where if they change your flight time significantly that you can cancel and/or pick a new flight, like US airlines? I know with Delta if they change a flight more than a couple of hours, you can rebook without penalty.

Book the budget airlines Vueling Easyjet early to get the best fares. I'm a frequent flyer of both they have early checkin a month or more before the flight. and you can print the passes or open it on your smart thingy if you download the aps.

Read all the rules and regulations when you book.

we can check in to our intra-Europe flight from the United States and print a boarding pass in the US several days before our flight, correct?

Yes, I think with easyjet it is up to a month in advance. Then when you arrive at the airport you can go first to bag drop if necessary (often self-service), then straight to security and the gate.

Do budget airlines allow digital boarding passes on smart phones like Delta, etc.?

Yes, if you have their app loaded.

do budget airlines like easyJet have a provision where if they change your flight time significantly that you can cancel and/or pick a new flight

Yes. There are also provisions that they have to feed and house you if a flight is delayed, and pay compensation. But sometimes they don't give out the compenstaion unless you know to ask. There is no responsibilty to pay for onward flights or hotel rooms you miss out on.

If you are taking any hold luggage, book and pay for that when you buy the ticket.
Or are you thinking of taking your one bag as hand luggage? If so remember one bag is just that, not one bag and a handbag.

Thank you again, everyone! I bought tickets this morning on easyJet, BCN to Geneva. Ended up being $61.50/pp including a fee for seat selection. easyJet did say I could check in up to 30 days before boarding so I will definitely do that and print our boarding passes from the US. I really appreciate everyone's help and advice! Y'all are the best!

The easy jet app is excellent and very easy to use. Also geo-fenced.

Also geo-fenced.

For the technology challenged, (i.e., me), what does that mean?