Born in Joplin, Missouri. Porter was drafted by the Milwaukee Brewers in the first round (4th overall) of the 1970 Major League Baseball Draft out of Southeast High School in Oklahoma City, OK. He made his major league debut on September 2, 1971, with the Brewers at age 19. He finished third in the Rookie of the Year voting. Porter was selected to the American League All-Star team in 1974. On December 6, 1976, the Milwaukee Brewers traded Porter along with Jim Colborn to the Kansas City Royals for Jamie Quirk, Jim Wohlford and Bob McClure.