Drabowsky made his major league debut on August 7, 1956, having just turned 21. He pitched a scoreless inning of relief in a 6–1 loss to the Milwaukee Braves. Eleven days later, pitching coach Dutch Leonard asked Drabowsky, "How would you like to do some throwing tonight?” "I'd like it," Drabowsky responded. “Then you’re starting against the Cardinals tonight.” Pitching into the eighth inning, Drabowsky held the St. Louis Cardinals to one run, picking up his first major league victory. He continued to make starts for the Cubs the rest of the year and finished the season with a 2–4 record, a 2.47 earned run average (ERA), and 36 strikeouts in 51 innings pitched.