Kores' professional baseball career began in 1910 with the Racine Belles of the Class-C Wisconsin–Illinois League.
He played just a month and a half with the Racine club, being used as a first baseman.
Kores spent his first full professional season with the Des Moines Boosters of the Class-A Western League in 1911.
With the Boosters, he batted .215 with 127 hits, 17 doubles, nine triples, and four home runs in 161 games played.
Defensively, he played all of his games as a third baseman.
After the season, Des Moines general manager Jack Holland attempted to trade Kores to another team, but no organization showed interest.

The day before the Des Moines Boosters opening series of the 1912 season, Kores signed a new contract with the team.
In his season debut, on April 19, Kores got three hits.
With Des Moines that year, he batted .298 with 182 hits, 25 doubles, 10 triples, and 10 home runs in 162 games played.
In the field, he played shortstop, committing 60 errors in 674 total chances.
At the end of the 1912 season, the Portland Beavers of the Double-A Pacific Coast League drafted Kores from the Boosters.
He was later drafted by the Chicago Cubs, but passed up the opportunity to play in Major League Baseball (MLB).

On March 1, 1913, Kores joined the Portland Beavers at their spring training camp in Visalia, California.
He played 165 games with Portland that season, batting .282 with 24 doubles, eight triples, and five home runs.
In the field, Kores played shortstop.
At the start of the 1914 season, Kores was moved from shortstop to third base.
During the season, The Milwaukee Journal described Kores as "the best clean-up hitter in the Coast league".
With the Beavers that year, he batted .296 with 54 doubles, 21 triples, and five home runs in 187 games played.
He led the Pacific Coast League in doubles, and triples that season.
Kores was also third in the league in runs batted in (RBIs) with 94 that season.

In September, 1914, the New York Giants drafted Kores from the Portland Beavers in what the Oakland Tribune a "secret lottery".
Kores rejected the Giants contract offer, stating that he could make as much money in the Pacific Coast League then he could in the majors.
He demanded a US$2,100 a year salary from the Giants, which New York declined to give him.
He eventually signed a contract with the Giants for an undisclosed amount.
According to Beavers officials, Kores, who told the Giants he was only 23 years old, had to confess his real age to get the contract.

Before the 1915 season, it was reported that the St. Louis Terriers of the Federal League were interested in Kores, whose contract was owned by the New York Giants.
At the start of the regular season, Giants manager John McGraw offered Kores' contract back to the Portland Beavers for a price of US$2,500, but Beavers manager Judge McCredie declined.
Instead, McGraw sent Kores to the Double-A Rochester Hustlers of the International League.
In 75 games with Rochester that year, he batted .275 with 76 hits, 11 doubles, 11 triples, and two home runs.
On July 23, it was reported that Kores had left the Hustlers to join the Major League St. Louis Terriers.
As a result, the Rochester club suspended him and fined him US$250.
Officials from the Hustlers said that it did not come as a surprise that Kores had left the team, because he was in talks with the St. Louis club for months.
Kores made his MLB debut on July 24, 1915.
With St. Louis that season, he batted .234 with 18 runs scored, 47 hits, nine doubles, seven triples, one home run, and 22 RBIs in 60 games played.
In the field, he played all of his games at third base, committing 10 errors in 251 total chances.

In 1916, the Federal League dissolved and the St. Louis Browns of the American League took over their operations.
The Browns then sold Kores to the Class-A Nashville Volunteers of the Southern Association.
With Nashville that season, he batted .275 with 117 hits, 21 doubles, and seven triples in 129 games played.
In the field, he played third base.
Kores re-signed with the Nashville Volunteers in 1917.
That year,
Kores' professional baseball career began in 1910 with the Racine Belles of the Class-C Wisconsin–Illinois League. He played just a month and a half with the Racine club, being used as a first baseman. Kores spent his first full professional season with the Des Moines Boosters of the Class-A Western League in 1911. With the Boosters, he batted .215 with 127 hits, 17 doubles, nine triples, and four home runs in 161 games played. Defensively, he played all of his games as a third baseman. After the season, Des Moines general manager Jack Holland attempted to trade Kores to another team, but no organization showed interest.
The day before the Des Moines Boosters opening series of the 1912 season, Kores signed a new contract with the team. In his season debut, on April 19, Kores got three hits. With Des Moines that year, he batted .298 with 182 hits, 25 doubles, 10 triples, and 10 home runs in 162 games played. In the field, he played shortstop, committing 60 errors in 674 total chances. At the end of the 1912 season, the Portland Beavers of the Double-A Pacific Coast League drafted Kores from the Boosters. He was later drafted by the Chicago Cubs, but passed up the opportunity to play in Major League Baseball (MLB).
On March 1, 1913, Kores joined the Portland Beavers at their spring training camp in Visalia, California. He played 165 games with Portland that season, batting .282 with 24 doubles, eight triples, and five home runs. In the field, Kores played shortstop. At the start of the 1914 season, Kores was moved from shortstop to third base. During the season, The Milwaukee Journal described Kores as "the best clean-up hitter in the Coast league". With the Beavers that year, he batted .296 with 54 doubles, 21 triples, and five home runs in 187 games played. He led the Pacific Coast League in doubles, and triples that season. Kores was also third in the league in runs batted in (RBIs) with 94 that season.
In September, 1914, the New York Giants drafted Kores from the Portland Beavers in what the Oakland Tribune a "secret lottery". Kores rejected the Giants contract offer, stating that he could make as much money in the Pacific Coast League then he could in the majors. He demanded a US$2,100 a year salary from the Giants, which New York declined to give him. He eventually signed a contract with the Giants for an undisclosed amount. According to Beavers officials, Kores, who told the Giants he was only 23 years old, had to confess his real age to get the contract.
Before the 1915 season, it was reported that the St. Louis Terriers of the Federal League were interested in Kores, whose contract was owned by the New York Giants. At the start of the regular season, Giants manager John McGraw offered Kores' contract back to the Portland Beavers for a price of US$2,500, but Beavers manager Judge McCredie declined. Instead, McGraw sent Kores to the Double-A Rochester Hustlers of the International League. In 75 games with Rochester that year, he batted .275 with 76 hits, 11 doubles, 11 triples, and two home runs. On July 23, it was reported that Kores had left the Hustlers to join the Major League St. Louis Terriers. As a result, the Rochester club suspended him and fined him US$250. Officials from the Hustlers said that it did not come as a surprise that Kores had left the team, because he was in talks with the St. Louis club for months. Kores made his MLB debut on July 24, 1915. With St. Louis that season, he batted .234 with 18 runs scored, 47 hits, nine doubles, seven triples, one home run, and 22 RBIs in 60 games played. In the field, he played all of his games at third base, committing 10 errors in 251 total chances.
In 1916, the Federal League dissolved and the St. Louis Browns of the American League took over their operations. The Browns then sold Kores to the Class-A Nashville Volunteers of the Southern Association. With Nashville that season, he batted .275 with 117 hits, 21 doubles, and seven triples in 129 games played. In the field, he played third base. Kores re-signed with the Nashville Volunteers in 1917. That year,
Art Kores