Cochran-Siegle learned to ski at around the age of two, being taught by his mother Barbara Cochran, gold medalist in the slalom at the 1972 Winter Olympics in Sapporo, Japan. After the 2010 season, he joined the US Development Team and one year later he was promoted to the National B Team. He was Nor-Am Cup Super-G champion in 2011 and took a bronze medal in the Super G at the US National Championships.
Cochran-Siegle made his World Cup debut in November 2011 at the Lake Louise Downhill, but failed to finish. A week later in Colorado, he scored his first World Cup points in a Super-G at Beaver Creek, finishing in 29th place.
In 2012, Cochran-Siegle won the Nor-Am Downhill and Super G titles, and he also took gold medals in the 2012 Junior World Championships in both the Downhill and the Combined. However his progress was interrupted when he suffered injuries to his anterior crcuiate and medial collateral ligaments whilst competing in the downhill portion of the Combined at the 2013 World Championships. He returned to competition in the 2014 season, winning the overall Nor-Am Cup and placing second in the Nor-Am Downhill and third in the Nor-Am Super G and Giant Slalom standings.
Cochran-Siegle took the 2015 season off to recover from a lateral meniscus transplant, before making his comeback in the 2016 season. During this season, he made his World Cup Giant Slalom debut, and took his first World Cup point in GS with a 30th place in a race at Kranjska Gora. He finished the season with good results at the US National Championships at Sun Valley, Idaho, where he was runner-up in the Super G and Giant Slalom and fourth in the Combined.In 2018 Ryan was a member of the United States Olympic team. He competed in multiple events including the super combine.