BALTIMORE (AP) -The Baltimore Orioles couldn't even win a series from the Tampa Bay Rays last season.

Now that they've gotten that accomplishment out of the way, the Orioles want more.

Baltimore won its second straight over the defending AL champions Saturday night, using a grand slam by Melvin Mora and a fine pitching performance by Jeremy Guthrie to carve out a 6-0 victory. After ending a 12-game skid against Tampa Bay on Friday, the Orioles clinched their first series win over the Rays since Aug. 3-5, 2007.

''I'm happy, but I'll be a lot more happy if we sweep,'' catcher Gregg Zaun said. ''We've got a second opportunity to sweep a ballclub in two tries. Hopefully we'll show up (Sunday) and put the finishing touches on it.''

Baltimore, which opened the season by taking two of three from the New York Yankees , is 4-1 for the first time since 2000.

Guthrie (2-0) allowed five hits and walked none in six shutout innings, and Mora's third career slam capped a five-run first against Tampa Bay rookie Jeff Niemann .

Nick Markakis had two hits and an RBI for the Orioles, who went 3-15 against the Rays last season.

Guthrie lowered his ERA to 2.25 and improved to 2-0 for the first time. His job was made easier by the five-run cushion he was given after retiring the side in order in the first inning.

''I expect the big hits from Melvin and everybody else,'' Guthrie said. ''He came through tonight and got us that big lead.''

Relievers Matt Albers , Jamie Walker and Chris Ray preserved Baltimore's first shutout of the season.

Evan Longoria went 2-for-4 for the Rays to up his batting average to .455. But his run of four straight games with at least one RBI ended, and Tampa Bay went 0-for-11 with runners in scoring position.

''We had some chances to get back into it, but we did not,'' manager Joe Maddon said. ''(Guthrie) made some good pitches when he had to. He pitched well. He had everything going on.''

The first six Orioles reached base against Niemann, the only rookie on the Rays' roster. Brian Roberts led off with a double and Niemann (0-1) hit Adam Jones with a pitch before Markakis doubled in a run. After Aubrey Huff walked, Mora hit an 0-1 pitch over the center-field wall, his first grand slam since June 2005, at Detroit.

''You know how hard it is sometimes to drive in one run? You knock in four in one shot, it's my week,'' Mora said.

Ty Wigginton followed with a single before Niemann finally settled down.

''It was a rough start. I had to go out there and keep trying to get guys out and let the defense work for me,'' Niemann said. ''I battled back, but I put us in the hole from the get-go.''

Guthrie, in contrast, retired the first seven Rays before Gabe Gross singled and took third on a double by Jason Bartlett . Gross was thrown out at the plate on a grounder by Akinori Iwamura , and Carl Crawford popped out.

Longoria and Carlos Pena singled to open the fourth, but Guthrie made sure neither advanced.

''He had to bear down and make some big pitches to get out of some innings,'' Orioles manager Dave Trembley said. ''He didn't flinch.''

Baltimore went up 6-0 in the sixth. Niemann was pulled after giving up successive walks, and Roberts greeted Brian Shouse with an RBI single.

Niemann made his major league debut last year, going 2-2 in five games. Both wins came against the Orioles.

Notes: The Orioles have scored 16 runs in Guthrie's two starts. ... Tampa Bay free agent pickup Pat Burrell was hitless in four at-bats and is batting .125 (2-for-16). ... After the game, optioned Albers to Triple-A Norfolk to make room on the 25-man roster for RHP Adam Eaton , who will start Sunday against the Rays.