Ross was the son of Ross II, who pitched for the 1951 Chicago White Sox, and his wife Judy Grimsley. Ross II, a World War II veteran, had a long minor-league playing career. The younger Ross Grimsley was a 1969 graduate of Frayser High School in Memphis, Tennessee, where he was an outstanding basketball and baseball player. He attended Jackson State Community College in Jackson, Tennessee. He was drafted by the Cincinnati Reds in the first round of the 1969 amateur draft.
Major league career
He made his major league debut for the Reds at age 21 on May 16, 1971 in a 9-3 loss to the Expos at Riverfront Stadium. He started and took the loss, pitched 1.2 innings and gave up three earned runs. The first major league hitter he faced was Ron Hunt. In 26 starts that year, he posted a record of 10-7 with a 3.57 ERA. He followed up with an even better season in 1972, going 14-8 with a 3.05 ERA for the National League champion Reds. He also had a strong World Series, going 2-1 in four games with a 2.57 ERA as the Reds fell to the Oakland Athletics in seven games. In 1973 he was 13-10 with a 3.23 ERA as the Reds won the NL West division. The Reds were well known for conservative appearance rules for its players. Flouting the team rules with long hair, he ran afoul of manager Sparky Anderson who requested after the 1973 season that Grimsley be traded. He, along with Wally Williams, was sent to the Baltimore Orioles for Merv Rettenmund, Junior Kennedy and Bill Wood two months later on December 4. The deal paid off for the Orioles in 1974 as Grimsley went 18-13 with 17 complete games in a career-high 39 starts as the Orioles were American League East division champions. In 1975 and 1976 his totals were down, with records of 10-13 with a 4.07 ERA and 8-7 with a 3.95 ERA. In 1977 he was 14-10 with a 3.96 ERA. He cashed in on his free agent status by signing a six-year $1.1 million contract with the Montreal Expos on December 6, 1977. The Orioles had attempted to trade him to the Expos for Barry Foote prior to the 1977 season. Grimsley rewarded the Expos with his best year in 1978. He was named to the 1978 National League All-Star team and finished seventh in voting for the 1978 National League Cy Young Award, posting a record of 20-11, 19 complete games, three shutouts, 263 innings pitched and a 3.05 ERA. However, in 1979 he fell to a record of 10-9 with a 5.35 ERA. In 1980 he was only 2-6 with a 6.31 ERA for the Expos, and on July 11 he was traded to the Cleveland Indians for whom he went 4-5 with a 6.75 ERA. Grimsley was released by the Indians and didn't play in the majors in 1981. In 1982 he returned to the Orioles, pitched 21 games in his final major league season. His career totals included a 124-99 record, 79 complete games, 15 shutouts, 2,039 innings pitched and a 3.81 ERA. Grimsley was one of the more colorful players of the 1970s. With the Reds, he was called into manager Sparky Anderson's office and told to stop corresponding with a "witch" who had been sending him good luck charms. In an incident on September 16, at Fenway Park, Grimsley, warming up in the Orioles' bullpen, responded to Boston fans' heckling by throwing into the right field bleachers. The ball passed through the protective netting, injuring a Boston fan. The fan later successfully sued Grimsley and the Orioles in Manning v. Grimsley, a case cited in law casebooks to highlight the scope of employment law as it relates to agency. He was accused by Yankees manager Billy Martin in 1977 of throwing "spitball" pitches using Vaseline hidden in his hair, which was usually somewhat greasy in appearance anyway due to Grimsley's penchant for not showering during winning streaks. In addition to his nickname "Scuz" for his grooming habits, he was also called "Crazy Eyes" for wearing turquoise contact lenses.