Peacock (4-1) struck out eight and held the Bowie Baysox to a pair of hits over seven innings in Double-A Harrisburg's 3-0 win, the Senators' second straight shutout.
The 23-year-old right-hander walked one and lowered his ERA to 1.16 in winning his fourth straight start. He's worked at least seven innings in each of the last three and ranks second in the Eastern League in ERA.
Peacock struck out five consecutive batters, spanning the first three innings. He's allowed one run on 10 hits while fanning 24 over 21 1/3 innings in his last three starts.
The Florida native held Altoona to a run over seven frames in his last start on April 28 after striking out nine over seven scoreless innings against Trenton on April 22. He gave up only three earned runs in his first two outings, winning one.
Selected by the Nationals in the 41st round of the 2006 Draft, Peacock totaled six wins all of last year between Class A Advanced Potomac and Harrisburg. He owned a 19-35 record over his first four Minor League seasons.
Pat McCoy struck out one in a perfect eighth and Ryan Mattheus worked a 1-2-3 ninth, fanning Robbie Widlansky to record his fourth save.
Derek Norris, the Nationals' top catching prospect, homered in the seventh and Bill Rhinehart went yard in the eighth to help Peacock secure the win.