Clark spent time with both the Rockets and Magic in 2019, appearing in 42 total contests. Clark began the year in Houston, where he saw action in 18 games, averaging 3.9 points and 2.2 rebounds in 11.7 minutes per contest. In a Nov. 27 win over Miami, Clark had 12 points and eight rebounds in 29 minutes. On Jan. 7, Clark was waived by the Rockets. He subsequently signed a 10-day contract with the Magic, later signing with the team for the remainder of the 2019-20 season. Clark made his debut for Orlando on Jan. 15 against the Lakers, when he finished with 10 points and four rebounds. In 12 games before the All-Star break, Clark averaged 3.1 points and 3.0 rebounds in 13.1 minutes per game. On Mar. 2 against Portland, Clark made his first start of the season, playing 29 minutes and finishing with five points, three rebounds, and one assist. In the NBA bubble, Clark started the Magic's final nine games of the season, including all five first-round playoff games against Milwaukee. During that span, Clark posted 7.2 points, 4.9 rebounds and 1.0 block in 28.3 minutes per game. In Orlando's Game 1 win over Milwaukee, Clark converted four three-pointers and finished with 15 points and six rebounds.

Gary Clark began his rookie season with the Rockets on a two-way contract and was ultimately converted to a full-time member of the NBA roster when he signed a three-year deal in December. Despite being undrafted, the Cincinnati product started the season in Houston. He appeared in 36 of the Rockets' first 52 games and scored 2.9 points per game. He then joined the Rio Grande Valley Vipers of the G League for four games. The forward rejoined the Rockets for their Feb. 11 win over Dallas. Clark followed a few DNPs with a breakout 14-point, five-rebound effort Feb. 28. In that game, Clark started for an injured Eric Gordon and helped Houston defeat the Heat. Clark spent March bouncing back and forth between Houston and Rio Grande Valley. Overall, he appeared in 51 NBA games, generating 2.9 points, 2.3 rebounds and 0.8 made three-pointers per contest. He also provided fiesty defense, with per-36-minute averages of 1.1 steals and 1.5 blocks. In the G League, Clark played in seven games, posting 12.0 points, 7.0 rebounds and 2.1 made threes per tilt.