Harris signed a minor-league contract with the Padres on Wednesday and debuted at Triple-A El Paso on Sunday, going 0-for-3 with a walk.
Harris, who elected free agency earlier in the month after opting out of a minor-league deal with the White Sox, will boost the Padres' organizational outfield depth. He's appeared in 17 big-league games this season across stops with the White Sox and Astros, hitting .233 with four stolen bases, five RBI and six runs scored.