When I was backpacking in Glacier National Park, most of the trails were sprinkled with thimbleberries. On our first day, I noticed these pops of red along the trail, but I had no idea what they were so I steered clear. (Note: We should NOT put anything wild into our mouths unless you're absolutely 100% sure it's safe to eat.)
My trail mate eventually verified that those red pops of color were thimbleberries and shoved a few into his mouth. My eyes grew big and I squealed with glee inside. I remember thinking, "Oh. GAME. ON." You see, I grew up eating lots of fresh fruit, but on the trail, I get maybe one apple on the first day. The rest of the time, it's rehydrated food. So getting any kind of fruit/fiber/freshness on the trail was going to be a huge win.
Let's just say that more often than not, I was holding up my group because I stopped to collect a mouthful of berries. (Sorry guys!) So, YES, thimbleberries are edible! But make sure you're 100% that's what you're eating.
Note: I'm not a naturalist or expert in plant identification by any means, so I'm not recommending anything here. This is simply an account of my experience of finding and eating wild edible thimbleberries. Don't sue me for your decisions! ;-)