The following season, Yarborough won nine races, including four in a row late in the season along with the Firecracker 400, in winning his first career Winston Cup Championship. He repeated his nine-win performance in 1977, a season in which he finished every race and did not finish outside of the top-six during the last fourteen races of the season, earning him his second championship. Another highlight of the season was his second Daytona 500 victory, earning him a cover appearance on Sports Illustrated, the second NASCAR driver so honored. He also scored two victories in IROC IV, finishing second in the standings. In 1978, his team switched to Oldsmobiles and received new sponsorship from 1st National City Travelers Checks. He matched his previous career high of 10 wins, including leading every lap of the Music City USA 420, his fourth Southern 500 and first Winston 500 at Talladega, and won his third consecutive championship (clinching it at the American 500). In IROC V he captured one victory, finishing fourth in the standings.