Gross was best-known for his clutch pinch-hits as a Phillie, and holds the Phillies career record in pinch hits with 117. He is also Major League Baseball's 5th all-time leader in career pinch hits with 143.
On June 4, 1970, Gross was selected by the Houston Astros in the fourth round of the free agent draft. He led the league in hits in 1970 while playing for Covington in the Appalachian League, batting .351. He also tied for the league lead in double plays by outfielders. In 1971, Gross was promoted to the Columbus Astros of the Southern League, where he played outfield and first base. In 1972, Gross played most of the season at Columbus, and was promoted later on in the season to the Oklahoma City 89ers, which was the Astros' AAA farm club. In 1973, Gross started the season with the Denver Bears, which by that point had become the Astros' new AAA farm club.
The Astros decided to call up Gross to the major leagues late in 1973. On September 5, 1973, Gross made his major league debut with the Astros, going 0-for-1 as a pinch hitter in a 9-3 loss to the Cincinnati Reds. Gross finished the season going 9-for-39 for a .231 average.
In 1974, Gross became the Astros' starting right fielder and leadoff hitter, playing in 156 games and batting .314. Gross was named the Sporting News' National League Rookie Player of the Year and finished second in the voting for National League Rookie of the Year. Gross also finished the season with a .393 on-base percentage, giving him one of the highest on-base percentages of any rookie since 1970. In 1974, Gross also set a major league record for most times caught stealing in a rookie season with 20. In 1975 and 1976, Gross continued to be a starting outfielder for the Astros, hitting .294 and .286, respectively.
On December 8, 1976, the Astros traded Gross to the Chicago Cubs for Julio Gonzalez. In 1977, Gross hit his first major-league home run, connecting a total of five times while hitting .322 in 115 games. After a busy 1978 season, Gross was traded by the Cubs on February 23, 1979 to the Philadelphia Phillies with Manny Trillo and Dave Rader for Jerry Martin, Barry Foote, Ted Sizemore, Derek Botelho and Henry Mack. Gross established himself as a key platoon outfielder and first baseman for the Phillies, getting to play in the 1980 League Championship Series (he went 3-for-4 -- all pinch hits -- with 1 RBI in 4 games), the 1980 World Series (he went 0-for-2 in 4 games), the 1983 League Championship Series (he went 0-for-5 in 4 games with a run scored), and in the 1983 World Series (he went 0-for-6 in 2 games). And, Gross was an invaluable pinch hitter as well. In 1982, he led the league in pinch hits with 19.
Gross has said he had hoped to be a full-time player for the Phillies in the late 1970s and early 1980s, but the Phillies just had too many other talented outfielders, namely Bake McBride, Greg Luzinski and Garry Maddox. "I...didn't figure I should be playing part-time at that point in my career," Gross told the San Diego Union-Tribune in an article that appeared on March 18, 1991. "But they had those three guys and I knew they should be playing ahead of me. Plus, they were winning and that changes your thinking a lot. Before, I was playing on second-division teams and we were out of it pretty early. But when you get your first taste of winning, when you're in the playoffs and the World Series, you want more of it." In addition, Gross acknowledged in an interview in 2007 the difficulty of being a starting player when he was neither fast nor a power hitter. "The cycle that baseball was in back then, with the AstroTurf and everything, centered on the stolen base or the home run, and I did neither of those," Gross told The Patriot-News of Harrisburg in an article that was published on April 8, 2007. "It was just a matter of survival. You made the best out of it. The big break for me was when I got onto a real good club."
Gross remained with the Phillies through the 1988 season, in which he hit just .203 in 133 at-bats but posted the unusual statistic of striking out just 3 times during the entire season. In fact, in Gross' entire career of 3,745 at-bats, Gross struck out just 250 times.
On April 5, 1989, Gross rejoined the Houston Astros as a free agent, hitting .200 for the season largely in a pinch-hitting role. Despite his historic success as a prolific pinch-hitter, Gross struggled as a pinch-hitter with the Astros in 1989, hitting just .184 (7-for-38). In October 1989, as part of a rebuilding movement, the Astros told Gross and many other veterans -- including Bob Forsch, Rick Rhoden, Dan Schatzeder, Terry Puhl and Harry Spilman -- that they would not negotiate new contracts with them before the free agent filing period, which was to begin after the 1989 World Series, if at all. On November 2, 1989, Gross filed for free agency. Gross had hoped to be invited to a major-league club for a tryout in 1990. After a lockout by the owners in early 1990, Gross never received a single tryout, and he wound up sitting out the 1990 season.
Gross again tried to extend his baseball career. On February 7, 1991, the San Diego Padres announced that they had invited Gross to spring training. Gross came to spring training at the recommendation of his old teammate and then-Phillies coach Larry Bowa, who had asked then-Padres manager Greg Riddoch to invite Gross to camp. "I love this game so much," Gross told the Los Angeles Times in an article that appeared on February 28, 1991. "I can't leave it alone. It's not the money. It's not the attention. It's just being around this game. And I'm not going to cheat myself from playing as long as someone will let me."
On March 30, 1991, the Los Angeles Times reported that Gross had made the Padres as a pinch-hitter. However, on April 5, 1991, the Padres cut Gross, choosing instead to sign Mike Aldrete to its final roster spot. The move ended Gross' major-league career. Several weeks later, there was reported interest in Gross by the Boston Red Sox, according to a May 14, 1991 article in the Boston Globe, but nothing ever materialized.
"I've enjoyed my career, I really have," Gross told the San Diego Union-Tribune in March 1991. "There've been frustrations, sure, but the good times and being at this level of the game outweigh any of the negatives. I wanted to play every day, sure, but it didn't work out for me. But I found that niche and it worked out. Probably, if I'd been an everyday player, I wouldn't have lasted this long. I'd rather have the longevity."
Both in 1986 and in 1989, Gross was called to the pitcher's mound during blowouts. On June 8, 1986, Gross pitched the final two-thirds of the eighth inning in a 12-0 Phillies loss to the Montreal Expos. Gross gave up a double to Andres Galarraga, and then struck out Casey Candaele and Herm Winningham to end the rout. And on May 21, 1989, Gross took the mound in the ninth inning of what wound up being a 17-5 loss by the Astros to the Pittsburgh Pirates. In that game, Gross had relieved shortstop Craig Reynolds, who had pitched the eighth inning. In the ninth inning, Gross gave up three hits and two earned runs. However, he also struck out Jose Lind swinging. "The worst part is how close you are to the batter after you throw the ball," Gross told the Sporting News in its June 5, 1989 issue. "I throw batting practice, but you've got the screen. I was looking for a way to sneak the screen out there."
After his baseball career ended, Gross worked as a color commentator for several games for SportsChannel Philadelphia in 1991. He also dabbled in real estate and coached high school teams like Malvern Prep High School. He returned to professional baseball on February 6, 1995, when the Colorado Rockies announced that Gross would make his debut as a professional coach with the Rockies' AA New Haven Ravens minor-league affiliate in New Haven, Connecticut. In 1995, Gross worked as a first-base coach for the Ravens, and then stayed with the club for the 1996 season as well. On October 24, 1996, the Rockies promoted Gross to become the Rockies' roving minor-league hitting instructor. He served in that capacity in 1997 through 2000. Gross quit the Rockies at the end of the 2000 season to become a bench coach for the Philadelphia Phillies in 2001. In 2002, Gross became the Phillies' hitting instructor. He remained the Phillies' hitting instructor through 2004.
On January 3, 2005, Gross became the hitting instructor for the Phillies' Class-A Batavia Muckdogs minor league team. On December 22, 2005, Gross was named the 2006 hitting coach for the Phillies' high-A Clearwater Threshers minor-league team. On November 28, 2006, Gross was named the hitting coach for the Phillies' Reading Phillies minor-league team. And on December 13, 2007, Gross was named the 2008 hitting coach for the Phillies' Triple-A Lehigh Valley IronPigs minor league team.
Gross has two children and lives in West Chester, Pennsylvania.
Gross is honored annually by the AGA with the Greg Gross Open (GGO) golf tournament held at the Anetsberger Golf Club in Northbrook, IL. The 2008 GGO will be held August 2. The reigning GGO champ is Scott Strangberg of Racine, Wisconsin.