Valparaiso (13-2) held the Dukes to 18 percent shooting in the first half to grab a 40-16 lead by halftime. Peters, with his second double-double of the season, and Keith Carter both scored nine in the first half as Valpo shot ahead 13-5, holding James Madison to two field goals in the first 11 minutes.
Winston Grays scored 14 off the bench to lead James Madison (7-6).
The Dukes hit just 13 of 55 shots in the game and were outrebounded 48-38.
Valpo's 6-foot-10 Vashil Fernandez blocked four shots, his seventh game with four or more this season.