An obvious stunt-doubled scene in particular is in season 1 episode 16 titled "The Links". You know the episode where the gang heads to Palm Springs for the weekend via Oliver's parents golf course mansion.
They started racing like a couple of gentlemen but Oliver quickly turns the race into destruction derby! At one point Oliver drives his golf cart almost into Ryan and Luke's causing their cart to go out of control.
If you look closely during the above fast action cut scene you will see a stunt-man in place of where Ryan was sitting in the golf cart. On the very right you will see where Oliver and Marissa's cart comes close to making contact. Wrist cuff check, opened button up shirt check, bad Ryan wig check, check! Our theory is that Benjamin McKenzie didn't want to risk his charming good looks too early in his career so he said Hey Josh Schwartz hook me up with a body double baby! Alternatively perhaps Ryan couldn't pull off those kinda crazy golf cart maneuvers and Josh Schwartz had to call in the big guns!
The stunt double/stunt driver for Ryan according to IMDB is Matthew Taylor, he was in three O.C. episodes. He has been a stuntman for 20+ years and has doubled for some big Hollywood names including Brad Pitt!
Interestingly enough during the golf cart stunt shots Chris Carmack appears to be riding as Chris Carmack. Although the IMDB page for this episode states the stuntman for Chris was Kanin Howell (8 O.C. episodes). We couldn't find any scenes in this episode showing the stuntman Kanin Howell unless they did an epic job at disguising him as Luke (which could be possible). #stuntlife.