Iberia has a great deal to Barcelona.
While January and February aren’t the best time to visit Barcelona, the weather is more mild than it is in the Northeast of the US (I once spent about 3 weeks there in January and it was comfortable enough). On the other hand, average highs in October are in the 70’s, so next October might be a great time to go.
As is frequently the case with LEVEL sales, the best fares are actually a combination of separate tickets. You can fly from Boston to Barcelona for just $84. The return flight is $100.
Check out all the details here: