Yes, assuming you have a 2007 OCR3 they fit. I have the Planet Bike Hardcore Road fenders on my OCR1 running Vittoria Randonneurs, 28s, and installed Planet Bike Cascadias on my gf's OCR3 with the stock Kendra tires, 26s. It is definitely a tight fit, and required one variation from the standard installation instructions, but they fit. Wonderful having full fenders.
I don't know about other year's models though. Looking at a 2008 OCR in my LBS it doesn't look like the frame has changed, but you never know.