I've done 10 RS tours and been vegan the whole time. In general the guides have been outstanding and able to get vegan food at nearly all group meals.
There have been the expected hiccups along the way as I found some countries have varying definition of what is "meat", lol. For instance on Village Italy there is a cooking class. I saw the guide discussing vegan with the chef. When the plates came mine and my brother's (also vegan) had the pasta sauce with wild boar because apparently boar is not a meat. We looked at each other and laughed, guide was upset but we told her not to worry....and we just ate what we could and fell back on Clif bars. In general the guides have gone above and beyond what I would have expected.
I took my first tour in 2013 and I feel like there is a huge improvement in understanding at least in France and UK. In fact, just finished Best of Scotland and a couple of places for group meals actually had separate vegan menus.
For the record, I've done:
Heart of Italy
Best of Ireland
21 day Best of Europe
Best of Paris
Best of England
Paris and Heart of France
Germany, Austria and Switzerland
Villages of Southern England
Best of Scotland
We also did the Villages of Southern England this spring. My routine is to go up to the guide after the first session, re-introduce myself and say something like "I'm your problem child with food I'm vegan". This tour my brother and my SIL's sis who are both vegan traveled as well so there were 3 of us. The guide was SO awesome. He said he nearly panicked when he saw he had 3 vegans because in his 30 years of guiding had never had anyone identify themselves as vegan. The meals went VERY smoothly and he was relieved. Afterward, the one he said he was most worried about was a pub lunch on Dartmoor with a set plate of a Ploughman's lunch with bread, salad and cheese. They gave us just the bread and an immense salad and we were happy as could be but he said he had no idea what to expect. We also told him we always carry some back up food just in case something doesn't work out.
I think the most difficult time was Best of Ireland. That was 2014 and I'm betting things have progressed. I've also learned a lot so I check menus ahead. If it doesn't look like a particular group restaurant will work, I try to sit on the end so I can excuse myself unobtrusively and go forage on my own.
By the way...I've also done 10 Road Scholar tours, 5 of them International - England, Wales and France and there has been no problem with group meals on any of them either.
What tour or tours have caught your eye?