Gray (7-3) snapped a two-start losing streak after giving up two runs on six hits and two walks while striking out seven.
Moss' RBI double in the fifth scored Yoenis Cespedes, who was one of four players with two hits for the A's in their fourth win in five games.
Nick Tepesch (2-3) remained winless in his last four starts, giving up all four Oakland runs on nine hits and two walks in five innings.
Shin-Soo Choo had two hits, including a two-run single for the Rangers, who have dropped three of their last four.
2014: The Year in Music [PHOTOS]