His poor record notwithstanding, he was taken from the Angels in the 1961 Rule 5 draft by another expansion team, the New York Mets, who were set to enter the National League in 1962.

But when Gatewood could not crack the Mets' maiden roster in spring training, he was offered back to the Angel organization, where he divided his 1962 campaign between Triple-A and Class B affiliates.

Gatewood spent the full minor league season of 1963 with the Double-A Nashville Vols, where he made 20 starts and posted a 3.95 ERA.

Gatewood had a shutout until the ninth inning, when Red Sox slugger Dick Stuart led off with a triple and scored two batters later on Russ Nixon's sacrifice fly.

His first two appearances as a Brave were effective ones; but in his third, on July 8, Gatewood allowed six runs (although only one was earned) in only one-third of an inning in a 13–0 pasting at the hands of the San Francisco Giants.