Dominique scored 21 in the second half to spark the rally. St. Peter's trailed 43-29 early in the period but erased the deficit at 49-all just before the 10-minute mark.
The Peacocks (13-13, 7-8 Metro Atlantic) continued to roll from there and went unchallenged in the final minutes, outscoring Niagara 50-26 in the second half.
Dominique was 9 for 9 from the field and 9 for 10 from the foul line. His only miss of the night came on a free-throw attempt with 1:08 left.
Niagara (4-20, 3-12) made just 8 of 26 from the field, including 1 of 10 from 3-point range, in the second half after going 12 of 22, with six 3-pointers, in the first. Dominique Reid led the Purple Eagles with 18 points.