The Orioles got home runs from each of the top third of their batting order, with Nate McLouth, JJ Hardy and Chris Davis all going yard.
That was enough to assure them of at worst a Wild Card spot after the Los Angeles Angels lost, and also kept them in a share of first in the American League East with the New York Yankees.
The Yankees also booked their post-season ticket by rallying from 5-1 down in the fifth to beat the Toronto Blue Jays 9-6.
The Angels were all but eliminated from contention after losing the second game of their double-header against the Texas Rangers, who sealed their post-season spot, 8-7.
Mike Napoli was the hero for the Rangers, homering twice and driving in six runs.
The loss left the Angels three games back on the Oakland Athletics, who occupy the second Wild Card spot, with three to play.
Earlier, Mike Trout, 21, became the first rookie and youngest player in MLB history to have 30 home runs and 30 steals in a season as he went yard in the Angels' 5-4 win over the Rangers in the day game.
Oakland reduced their magic number to one with a 5-2 win over the Seattle Mariners, Yoenis Cespedes homering the go-ahead run in the eighth.
The A's sit two games back on the Rangers with three games remaining in the AL West.
Prince Fielder put Detroit on the brink of the AL Central title as his eighth-inning homer gave the Tigers a 2-1 win over the Minnesota Twins.
Their lead over the Chicago White Sox stands at three with three to play after the second-placed side's woeful late-season form continued with a 6-2 loss to the Tampa Bay Rays.
The Washington Nationals were once again made to wait for the chance to become National League East champions as Carlos Beltran's pair of two-run shots gave the St Louis Cardinals a 10-6 win.
The Cards occupy the second NL Wild Card spot and remained two clear of the Los Angeles Dodgers, who beat the Colorado Rockies 7-1.
Matt Kemp, Luis Cruz and AJ Ellis all homered.
The Atlanta Braves, already assured a Wild Card spot, kept their theoretical hopes of catching the Nationals alive by setting an MLB record in their 6-2 win over the New York Mets.
It was the 23rd consecutive game started by Kris Medlen they had won, beating the previous mark of 22.
Jordan Lyles threw a complete-game shut-out, allowing just four hits and a walk, as well as crushing his first career home run in the Houston Astros' 7-0 win over the Milwaukee Brewers.
Asdrubal Cabrera hit a grand slam as part of a 10-run fifth as the Cleveland Indians beat the Kansas City Royals 15-3, while the San Francisco Giants were 7-5 winners over the San Diego Padres.
The Philadelphia Phillies beat the Miami Marlins 4-1, the Cincinnati Reds saw off the Pittsburgh Pirates 4-3 and the Chicago Cubs claimed a 7-2 victory over the Arizona Diamondbacks.