renting a car in Portugal and returning in Spain?

Go to Priceline and put in your itinerary and you will get some pricing. It is typically more expensive to rent in one country and drop in another.

Renting in one country and returning in a second is quite expensive because of the $400-500 drop off fee. I would suggest calling AutoEurope and speaking with one of their helpful associates. I rented a car in Madrid and returned it in Lisbon. The agent found one with a drop off fee of $375 which was worth it to me because of my itinerary. The train would be your most economical option.

I just went through this exercise but the other way-Seville to Lisbon, and Porto to Santiago. The drop fees(this was for September 2016) were obscene--in the neighborhood of +€750! In the first case, settled for flying for under €125 on way, and in the second, hiring a driver for €290 to take us and another couple. EU company's don't seem to want their cars to leave their particular country.

Thanks for the suggestions. We are going to use the train and rent a car for day trips around certain destinations within each country.

We had a taxi take us from Porto across the border to Vigo to pick up a Spanish rental car. We had turned in our Portugese rental when we arrived in Porto. Our hotel found us a good deal with a taxi to do this, much less than we had dound searching online before we left home.