The move was the first major league trade under new Dodgers president of baseball operations Andrew Friedman, who spent 10 years in the Rays' front office.
Peralta, 38, pitched 69 games for the Rays last season, going 3-4 with a 4.41 ERA. In 10 seasons with five teams starting with the Los Angeles Angels, Peralta has a 3.92 ERA and 1.18 WHIP.
The Rays recently picked up a $2.5 million option on Peralta for 2015.
"Joel's significance to the Rays transcended his on-field performance," Rays general manager Matt Silverman said in a statement. "He was a clubhouse leader who always sought ways to make the organization better."
Dominguez, 24, was among the hardest throwers in the Dodgers' organization. He pitched in 14 games over the past two seasons, with a 6.14 ERA.
Harris, 20, was 7-6 with a 4.45 ERA at Class A Great Lakes last season.
Liberatore, 27, was drafted in the 21st round by the Rays in 2010. He went 6-1 with a 1.66 ERA at Triple-A Durham.
The Dodgers invested heavily in their bullpen last winter, but it proved a disappointment in the regular season -- ranking 12th in the National League with a 3.80 ERA -- and a major liability in the playoffs.
The Rays also designated veteran catcher Jose Molina for assignment.
Reliever Peralta Heading To L.A.
Jerry Crasnick discusses how Dodgers president of baseball operations Andrew Friedman's familiarity with the Tampa Bay Rays' organization likely contributed to the trade that brings reliever Joel Peralta to Los Angeles.