Beltre and Moreland connected for solo homers that gave the Rangers their fifth win in their last six games.
Moreland, who also had a home run earlier in the game, followed Beltre with his ninth homer of the season and sixth in May.
Nelson Cruz had two RBI for the Rangers and Tanner Scheppers (3-0) picked up the win in relief.
Chris Resop (1-1) served up both home runs in the 10th and took the loss, Oakland's seventh in nine games. It was the first loss for A's bullpen this year.
Seth Smith had three hits, an RBI and scored two runs for Oakland. The A's Nate Frieman also had three hits and an RBI.