The free-agent right-hander, concluding months of speculation, agreed Tuesday to a one-year contract with the Rangers, according to a major-league source.
The last hurdle for the Rangers was ownership approval; the team was over-budget, with a $120.5 million Opening Day payroll that ranked sixth in the majors.
However, the Rangers’ average attendance has increased from 36,382 last season to 43,818 through 24 games — second only to the Philadelphia Phillies.
The deal, which was first reported by the Dallas Morning News, will be for between $5 million and $6 million, guaranteed, according to a major-league source.
The Rangers, who passed on Oswalt in spring training due to their surplus of starting pitchers, recently lost right-hander Neftali Feliz, creating an opening in their rotation.
The expectation is that Oswalt, 34, will be ready to pitch in the majors in three to four weeks.
He had a 3.69 ERA in 23 starts for the Phillies last season, but twice went on the disabled list with back trouble.
The Rangers’ interest stems in part from Oswalt’s prior relationship with club president Nolan Ryan, and perhaps received a final push when the Los Angeles Angels lost right-hander Jered Weaver to an apparent back injury on Monday night.
By signing Oswalt, the Rangers effectively would stage a preemptive strike on the Angels, preventing their principal division rival from acquiring the free-agent pitcher.
The Boston Red Sox, Philadelphia Phillies and Los Angeles Dodgers also have shown interest in Oswalt. The Phillies are awaiting word on the condition of right-hander Roy Halladay’s shoulder, and the Dodgers recently put lefty Ted Lilly on the disabled list with a shoulder injury.