He played in 146 games, starting 127 of them as either Washington's center fielder or right fielder. At the plate, he set personal bests in home runs (16) and runs batted in (59), while hitting a robust .276, second on the team to slugger Frank Howard's .278. He led the Senators in runs scored (77), hits (140) and doubles (29).
Then, in 1967, Valentine returned for another season as the Senators' "fourth" outfielder: he played in 150 games in all, and got into 136 games as an outfielder with 111 starts, most of these coming in center and right fields. However, his offensive production fell off in every category, as he hit .234 with 11 home runs. Returning to Washington in 1968, he appeared in 26 games in the outfield during the season's first two months.