How does checked-in baggage work with layover/multiple airlines?

Will be flying to Romania. I start with Iberia Airlines and layover in Barcelona for about 2 hrs. Then I fly to Bucharest with Blue Air.

Normally when flying with layovers, it's one airline so I know it's forwarded to my final destination. But this is my first itinerary where I switch airlines at my layover; would that mean my baggage is forwarded to Blue Air anyways, or do I need to pick it up and check it in a second time?

The incoming airline will transfer it right to the outgoing airline…

You'll have to pick it up and check in again.

It depends on the relationship between the two airlines. Usually, the first place you check in will check it all the way through to your final destination. But I had an experience in Singapore where my incoming airline didn't have a "relationship" with Delta, which I was flying back to the States. I had to pick up my luggage and check it back in. Your initial airline can tell you whether they are able to to check your bags all the way through.

If you booked those flights together, on a single itinerary, then the airlines are likely cooperating with each other and your bags will be transferred for you. You can find out for sure when you check your bags at your departure airport.

It does not appear that Blue Air Airways is a Codeshare with Iberia, so the chances are you will need to treat these as two separate flights. It also appears that Iberia operates out of T1, and Blue Air operates out of T2 so you will need to exit the terminal and take the shuttles to the next terminal.

So 2 hours for the layover, may be okay if everything works perfectly. But if your first flight is late or there's some other issue you may end up missing your second flight. So I would look at finding a different set of airlines or an itinerary that gives you more time between the flights.

In fact if time allows, I would suggest planning to stay a day or two in Barcelona. There are so many things to do and experience it can be a very good idea for a short stay-over.

Suggest you ASK when you check in if you need to claim your bag and recheck it or if it will forwarded for you.
At this time their is no agreement by Iberia Airlines to forward bags to Blue Air.

Your layover time is pushing the limits. You DO NOT have some Guaranteed to the minute arrival time of your first flight.

Depending how your purchased these two flights Blue Air does not have to provide a free room or some second flight if you miss the connection.

The time for your to get from one terminal to the next has take in time to walk to the shuttle bus and wait for next bus and them a wait in a security line for second flight.

You might make it but not guaranteed. It is prudent to allow more time.

No one can guess how minutes it will take you to get off first plane and walk to the transfer bus stop. If you need to wait for luggage that can be 15-30 minutes after arrival. Your bag might be first off or last one off.

DO NOT ASSUME Iberia will transfer your bag.ASK THEM.