Lopez, who had missed five straight games with a sore hamstring, led off the seventh by knocking a 0-1 pitch from Aaron Fultz (1-1) into the left-field stands.
Gary Sheffield also homered for the Braves, who extended Texas' longest losing streak of the season to six games.
Atlanta starter Mike Hampton left the game in the second with a strained groin, but six relievers limited the Rangers to only one run over the final 7 1-3 innings.
Jung Bong (5-0) got out of a bases-loaded jam in the seventh after the Rangers tied it at 4 on a run-scoring double by Juan Gonzalez. Third baseman Vinny Castilla leaned into the stands to catch a foul popup, then Donnie Sadler flied out to center to end the inning.
Lopez put the Braves ahead for good with his 14th homer. Atlanta poured it on in the eighth with three runs against R.A. Dickey.
Sheffield homered for the second game in a row, a 419-foot drive over the center-field wall that gave the Braves a 1-0 lead in the first.
Hampton was charged with three runs during his brief appearance, but none of them was earned because of an error by shortstop Rafael Furcal to start the second.
Furcal bobbled a grounder by Mark Teixeira, who came all the way around to score on Ryan Christenson's double. Todd Greene grounded out and Sadler walked before pitcher Victor Santos put down a sacrifice bunt.
Hampton apparently injured himself on the play, pulling up as the ball rolled toward the mound. First baseman Robert Fick got the out and Hampton left the game after a brief conversation with the trainer and manager Bobby Cox. The left-hander was listed as day-to-day.
Hampton started the season on the disabled list with a strained right calf. He was activated April 19.
Trey Hodges, who replaced Hampton, allowed a two-run single to Hank Blalock that put the Rangers ahead 3-1.
Santos, who was called up from the minors before the game, couldn't hold the lead.
Lopez sparked a three-run outburst in the fifth with a leadoff single. Santos walked Darren Bragg, batting just .136 coming into the game, before pinch-hitter Matt Franco blooped a single to drive in a run.
Furcal followed with an RBI single to left, tying the game at 3. Marcus Giles put the Braves ahead with a groundout that allowed Franco to trot home from third.
Notes: Santos started in place of Joaquin Benoit, who went on the DL with soreness in his elbow. ... Rangers 1B Rafael Palmeiro was scratched from the lineup after his back stiffened up during batting practice. The latest member of the 500-homer club failed to hit one out during the interleague series in Atlanta. ... Braves CF Andruw Jones continues to be sidelined by several nagging injuries. He didn't start for the fourth game in a row. ... Furcal was thrown out attempting to steal for the first time this year. He had been successful on 11 straight attempts before being called out on a disputed play at third. TV replays showed Furcal got a hand on the bag before Blalock made the tag.
http://accesswdun.com/article/2003/6/177753