Beltre hit .276 with 20 homers and 76 RBIs in 100 games before he strained his left hamstring running the bases against Toronto on July 22. Blanco, a utility infielder, has been on the DL twice since July because of lower back issues.
Texas, which now has 30 players on its major league roster, also completed its trade for Gonzalez when the Orioles acquired right-hander Pedro Strop on a waiver claim.
In other moves on the day that major league rosters could expand to 40 players, the Rangers purchased the contracts of infielder Esteban German and right-hander Merkin Valdez from Triple-A Round Rock. Infielder Omar Quintanilla was outrighted to Round Rock, which opens the Pacific Coast League playoffs next week.
Beltre was 2 for 8 in two games on an injury rehab assignment for Round Rock this week. He was out of the Rangers lineup twice as long as expected after he aggravated his injury during a running session last month.
Blanco was placed on the disabled list Aug. 9 with lower back inflammation, and was also on the DL July 7-30 with a stress reaction in his lower back. Blanco batted .206 with two homers in 28 games for the Rangers this season.
The Rangers reacquired Treanor, a catcher for their AL pennant-winning team last season, from Kansas City for cash. He missed all of August for the Royals after being placed on the concussion disabled list.
Gonzalez was 2-2 with a 4.27 ERA in 49 relief appearances this season for Baltimore. The left-hander made 13 consecutive scoreless appearances since July 22, allowing only five hits over 12 1-3 innings in that span.
Strop was 4-4 with 11 saves and a 3.59 ERA in 39 relief appearances for Round Rock this season. He was 0-1 with a 3.72 ERA in 11 games with Texas before being optioned to the minors May 4.
German hit .301 in 123 games for Round Rock. Valdez signed a minor league contract with the Rangers on July 24, and was 1-0 with four saves and a 2.35 ERA in 12 relief appearance for the Express.
Quintanilla cleared waivers and was outrighted off the 40-man roster.