Gluten free eating

I am here in Spain. There are several GF blogs you can check out and other Google searches. Spain has more education about GF but not always easy. Some things will come lightly breaded and I am not sure whether meat sauces are thickened with flour or just reduced. Occasionally menus identify what is GF....called 'celiaco' in Spain. If it os just wheat that is the issue, that is 'trigo' in Spanish.
I recommend asking for directions to a Carrefour Express. You may want to stalk up on some back up items from there. They have a small celiac section as well as lactose free. Personally, I can take a little wheat and oats, but I expect you have more experience ordering in restaurants for your level of tolerance. Breakfast is going to be hardest as this is a 'coffee and a roll' mentality with a small sandwich part way through the day. Tapas are frequently on bread and it is served at meals. When I travel personally, I get apartments so I can handle my own food as I have other fòd sensitivities as well.
If you haven't told them yet, do pass the info to the tour company and have a chat with the guide as soon as you meet. If this is a RS tour, they will be well versed with eating issues and can help.

Maria's post has reminded me that the tapas not sitting on bread are often battered and fried. But they are often out on display, so you can often see for yourself.

Lots of bars (typically open in the morning for the coffee-and-a-roll crowd) will have a "tortilla" out on the counter. In Spain that's a thick omelet-like egg dish served in slices. The ones I saw appeared to be gluten free; I'm assuming there's no gluten in potatoes. You'll want to have them heat the tortilla; it tends to be very bland if served at room temperature.

You'll find salads containing some form of protein (ham, tuna, and/or some sort of cheese) pretty widely available. They're often not prepared with much finesse, but most will be safe for you. I don't know what's in the white rind on the goat cheese, however. You can frequently find carry-out salads at the same places where you see sandwiches displayed.

Of your countries I have only been to Spain while my son has been gluten free. In restaurants it is good to have a card with an explanation of gluten free written out in Spanish. Most places will have some good options - and if you search ahead of time you can find out about restaurants that specifically list celiac items. Schar (the gf food brand) has a website that lists gluten-free friendly stores and restaurants link here The parador hotels and restaurants have gluten free selections marked on their menus. Fast food restaurants like VIPS sandwiches, Telepizza, and McDonalds have gluten free buns/pizza crusts (if you ever need, not to seek out specially as these are fast food and not great cuisine. But sometimes you are in a hurry!). Here is a blog with more info link here
Only once did my son need to have a meal of jamon and a cheese plate because there wasn't a better choice - and he was happy with this!
In Nerja there were paella stands lining the beach and a couple specifically said the paella was gluten free. I think paella would always be, unless a stock with flour thickener was used.

Grocery stores will be good as well. Anywhere you can find things like fruit and yogurt - good to have for a snack. And deli meats, cheese and drinks. Bigger stores, and many smaller ones, will have boxes of gluten free cookies, snacks, granola bars, etc. I'd pick up a few things when you see them.

you might want to do a search for previous posts/topics ( in the search bar at the top of the screen) for gluten free. as it has been covered before in detail. we find france as ' sort of ok' for gluten free meals, if you really look for them and for foods in the supermarkets. not as easy as italy. ( we spent another month in regional france this year)
hope this helps.

Jane, are you going to Cordoba in Spain? I just had a great gluten free meal in Mercado Victoria. Many of the old markets have become food stalls, but with good food and drink. The stall is Venezuelan food called Arepa's Come & Calle. I hate patacone which is a flattened plantain topped with loads of fresh goodness, and Arepas are smaller round 'breads' stuffed stuffed like a taco. They may have corn in them so ask if this a problem for you. Youmay want to keep an eye out for these types of mercados tobuild a meal from. A bit from here, a bit from there and a cervesa from somewhere in between.