The victory was big for the Red Sox as it clinched home-field advantage throughout the American League playoffs, which start next week. Boston improved to 106-51, breaking the franchise's single-season wins record.
Betts finished 2-for-5 with two RBIs plus a stolen base, his 29th of the season, and now he has a major-league-leading .343 average. Andrew Benintendi went 2-for-4 with one RBI and his 21st steal.
For Eovaldi, two wild pitches in the fifth were the lone blot on his record, as they helped Baltimore (45-111) to its first run. However, the Orioles couldn't do much more.
For Baltimore starter Dylan Bundy, though, the problems that have plagued him through the last few months continued in this game. Bundy (8-16) labored through three innings, throwing 90 pitches and giving up four runs on five hits with three walks and five strikeouts.
The Red Sox took charge of this game to take a 4-0 lead in the second inning.
Steve Pearce and Brock Holt hit back-to-back, one-out doubles that gave Boston a 1-0 lead. Christian Vazquez followed with an RBI single, and Betts later belted a two-run homer on top of the Green Monster in left that gave Boston a 4-0 edge.
In the fourth, against left-hander Donnie Hart, Benintendi made it 5-0 on an RBI infield single. Xander Bogaerts added an RBI single later in the inning for a six-run advantage.
Baltimore finally scored in the fifth when Tim Beckham came in on one of Eovaldi's wild pitches. Adam Jones added another run in the eighth on a sacrifice fly.