Gabe Speier competed at Cooperstown Dreams Park in 2007, Tournament 10 with the Santa Barbara Islanders (CA). He helped his team to an undefeated pool play record for the 7th seed and reached the Sweet 16.

Gabe graduated from Dos Pueblos High School (Goleta, CA). A left-handed pitcher, he led his varsity baseball team to a league title with 87 strikeouts and a .412 batting average his senior year. Gabe earned Channel League MVP in 2013.

Gabe committed to play baseball at UC Santa Barbara (Santa Barbara, CA), however, he was selected by the Boston Red Sox in the 2013 Major League Baseball draft and opted to begin his professional career. After just one season, he was traded to the Detroit Tigers (December 2014) then the Arizona Diamondbacks (November 2015). In June of 2018, Gabe was sent to the Kansas City Royals where he made his Major League debut on September 5, 2019. The Seattle Mariners signed Gabe in November 2022 and he helped the franchise clinch the 2025 American League West division.

Gabe was also a member of Team USA for the 2026 World Baseball Classic.