Justin Duchscherer (2-1) allowed six runs -- only one earned -- and six hits over five innings with six strikeouts in his 200th major league game and eighth career start. The right-hander, making his second start after missing three weeks with a biceps strain, ran his career record against the Angels to 6-0 -- although four of those wins came in relief.
The A's, who beat the Halos 14-2 in Monday's series opener, had 20 hits. Frank Thomas, Bobby Crosby, Daric Barton, Ryan Sweeney and Kurt Suzuki each had two RBIs and Cust scored three runs.
Cust, whose two-out error fielding error in left field led to five unearned runs in the Angels' second inning, gave Oakland a 7-6 lead in the fifth with his second homer of the season and first in 40 career at-bats against Angels pitching.
Los Angeles was the only AL opponent Cust had never homered against.
Thomas and Crosby each hit two-run singles during a 49-pitch meltdown by Angels relievers Dustin Moseley, Darren O'Day and Chris Bootcheck, which included a wild pitch by Bootcheck that accounted for the eighth and final run of the inning.
Oakland took a 6-5 lead in the fourth with the first of Barton's two RBI singles. Mike Napoli tied it in the bottom half with his sixth home run.
Los Angeles starter Nick Adenhart, called up from Triple-A Salt Lake after middle infielder Maicer Izturis went on the disabled list with a strained lower back, gave up five runs, three hits and five walks over two-plus innings in his major league debut.
The 21-year-old right-hander, who has replaced Phil Hughes of the Yankees as the youngest player in the majors, was 4-0 with a 0.87 ERA in five starts with the Bees. His overall record in the minors is 32-15.
Pitching on three days' rest, Adenhart got the side out in order in the first but walked four consecutive batters during Oakland's four-run second. Brown singled and scored the first run on a wild pitch to Jack Hannahan. Sweeney, the A's No. 9 hitter, drew a bases-loaded walk, and Suzuki followed with a two-run single inside third base.
Of Adenhart's 37 pitches that inning, 24 were balls. But the Angels grabbed a 5-4 lead in the bottom half with five unearned runs. Cust opened the door with a humiliating two-base error, as Garret Anderson's lazy flyball popped out of his glove when he camped under it.
Robb Quinlan then reached on an infield hit, and Napoli followed with an RBI single. Erick Aybar, the Angels' No. 9 hitter, drove a 2-0 pitch to right-center for his first homer of the season on Duchscherer's 24th pitch of the inning that tied the score. Chone Figgins reached on a bunt single, stole second and scored the go-ahead run on a single by Gary Matthews Jr.
Moseley, whose switch to the bullpen earlier this week forced the Angels to pluck Adenhart from the minors because of their need for a fifth starter, came on and gave up a single to Cust that loaded the bases. One out later, Hannahan hit a sacrifice fly to tie the score at 5-all.
Notes:@ A pregame moment of silence was observed in memory of former Angels vice president and general manager Buzzie Bavasi, who died Thursday at age 93. Gene Autry hired Bavasi in 1978, and the Angels won two division titles while he was there. But in 1979, he wasn't able to re-sign Nolan Ryan because Autry had turned down agent Dick Moss' request for the club to take out a life insurance policy on Ryan that would have cost the team $135,000. Ryan ended up signing with Houston as a free agent, becoming baseball's first million-dollar player. Bavasi's comment was: "We'll just have to find a couple of 8-7 pitchers to replace him." ... Cust started in LF for the 14th time this season. Last year he started 12 games there, 46 games in RF and 56 games as a DH while leading the A's with 26 homers and 82 RBIs. ... Angels INF Matt Brown drove in a pair of ninth-inning runs with a double, his first major league hit.