Earl began racing in Formula Ford in 1972 and won the national championship in 1973. After several years developing his craft, he made his professional debut in Formula Atlantic in 1979. His open-wheel peak came in 1981 when he became the first American to win the prestigious Macau Grand Prix, driving a modified Hayashi 320 at a time when the race was contested with Formula Atlantic machinery. The victory was a significant milestone in both his personal career and for American representation at the internationally prominent street circuit event.
Earl transitioned to sports cars in 1985, joining Huffaker Racing to drive a Pontiac Fiero in the IMSA GTU class, where he competed for two seasons. In 1986 he moved to prototype machinery, driving for Spice Engineering in the GTP class. The partnership with Spice quickly yielded results: Earl and the team claimed a class victory at the 24 Hours of Daytona in 1987, one of the landmark endurance events in American motorsport. He continued in the GTP class with Spice through 1988.
In 1989, Earl switched to Roush Racing's Lincoln-Mercury programme in the GTO class and captured class honours at Daytona once again, demonstrating his ability to perform in marquee events regardless of manufacturer or machinery.
Earl's career reached a new level in 1990 when he joined the Nissan GTP factory team. Racing with one of the most competitive prototypes in IMSA, he captured three victories that season — at the 12 Hours of Sebring, Miami, and Watkins Glen — as part of Nissan's factory assault on the championship. He remained with the Nissan programme until the manufacturer withdrew from the series after the 1992 season.
For the 1993 season, Earl competed in the Camel Lights prototype class in an Acura-powered Spice, adding two more wins before retiring from competition at the season's close.
After stepping back from racing, Earl became a driver coach. In 1996 he was hired to establish the Derek Daly Academy at Las Vegas Motor Speedway, helping to develop the next generation of racing talent. By 2000 he returned to the San Francisco Bay Area to resume freelance driver coaching. From 2002 to 2009 he served as Technical Director and oversaw the Mechanics Training Programme at the Jim Russell Racing School at Infineon Raceway in Sonoma, California.
Earl also developed the "Virtual Racing Chassis," an advanced racing simulator designed for use with racing video games, extending his expertise into the sim racing world.
He later became involved in environmental activities in Humboldt County, including restoration of beach dunes and redwood forest trails.
Bob Earl's racing career was defined by his consistency across categories and eras. His 1981 Macau Grand Prix victory marked him as a pioneer for American drivers on the international Formula Atlantic stage. His sustained success in IMSA — from Daytona and Sebring class victories to wins on street circuits and road courses — placed him among the solid core of American sports car professionals during the sport's most competitive domestic era. His post-racing contributions to driver development through coaching and education extended his influence well beyond his years as a competitor.