Morse began the season on the disabled list with a strained back muscle. He missed Washington's first 50 games before coming off the DL on Friday.
To make room for Morse, the Nationals optioned outfielder Corey Brown to Triple-A Syracuse. Brown played in three games with Washington after having his contract purchased from Syracuse on May 26.
The 30-year-old Morse batted .381 in seven rehabilitation games in the minor leagues. He hit .303 with 31 homers and 95 RBIs in 146 games with the Nationals last year.