He graduated from the University of Southern California and played in the majors from 1960 through 1970, initially signing with the Milwaukee Braves in 1959 as an amateur free agent.

After parts of three seasons with the Braves, he was traded to the Chicago Cubs on June 3, 1964, in exchange for catcher Merritt Ranew and $40,000.

The Giants received Gabrielson and catcher Dick Bertell, in return for Harvey Kuenn and Ed Bailey and pitcher Bob Hendley.

He led the team in home runs with ten in 1968, an unusually low total made possible by league-wide offensive declines that season, the so-called "Year of the Pitcher".

His father, Leonard Hilbourne Gabrielson, was also an MLB player, having spent part of the 1939 season with the Philadelphia Phillies.