In a corresponding move the Rockies optioned reliever Gonzalez Germen to Albuquerque.
Gray, 23, was the third overall pick in the 2013 draft. He was 6-6 with a 4.33 ERA in 21 games -- 20 starts -- for Albuquerque this season. In his last six starts he is 3-1 with a 2.70 ERA and 38 strikeouts.
Gray is the first Rockies starter to make his major league debut this season and the fourth in the past two seasons. He is Colorado's highest draft pick since right-hander Greg Reynolds was taken second overall in the 2006 draft.
Colorado also outrighted left-hander Aaron Laffey to Triple-A.
The Rockies have a full 40-man roster.