air consolidators for spain trip in May-June

Skyscanner.com is a good place to research fares and schedules.... suggest buying direct from airlines

No one site covers all fares. The most comprehensive I know is matrix.itasoftware.com

Operated by Google for the airlines, it is good for planning efficient multi-city itineraries. It does not sell tickets but the information is useful for going to the sites that do.
Skyscanner is very good for one-way budget fares in Europe but not so competitive on trans-continental fares. It links to the airlines which sell the tickets directly.

I second Joe. Check the search engines and then buy from the airlines directly. Many posters who have bought from consolidators have reported of trouble they've had when trying to resolve issues if you are not able to travel. Have fun

Agree with Southam. Also, consider all sorts of permutations. Typically, I find the best airfares from my remote location as R/T or open jaw to a few major cities (e.g. Frankfurt), and book separately tickets on budget airlines operating within Europe or hop the train.

EDIT: Strongly suggest you book tickets directly rather than through third parties. It's much easier to walk up to customer service counters at airports and fix problems rather than dealing with a third party via long distance, Also, if you have separate tickets for travel within Europe shortly after arrival, account for possible delays.

I would use google flights to check airfares. If you know your exact dates, you can check fares now into/out of Barcelona. You may want to consider flying into/out of Madrid as the airfares right now are about $250-$300 cheaper per person. You can take a train to Barcelona from Madrid. Also, where will you begin and end your trip? If you are not required to fly into/out of Barcelona, consider an open-jaw flight.

In regards to what Bruce said above, Norwegian has very inexpensive fares direct from Denver to London and Paris now. You might price them and a budget European airline on skycanner from those cities to Barcelona.

You could fly Norwegian Air Shuttle into London Gatwick where all the budget airlines fly out of. You could fly into Barcelona from there.
Another option after 4/7/2018 would be to fly into Paris, tour there for a couple of days and then catch one of the very fast trains into Barcelona.

Yes, do seriously consider Norwegian, and do read the fine print.
If you do take them, give yourself a minimum of 3 hours between flights. If they change their flight time, they will not do anything to help you with that connecting flight that you might miss. (This happened to me, but I still recommend them!)

Are you bring you own bikes? If so, you need to check the fine print for oversized luggage if not using a suitcase bike. The oversizing fees can be substantial and the discount airlines tend to charge more.