The Bulldogs (16-5, 8-2 West Coast) stormed ahead early and led by as many as 29 in the first half. Wiltjer had 23 points before the break, one more than the Broncos (7-15, 3-7) who trailed 46-22.
Gonzaga outrebounded Santa Clara 27-12 in the first half.
Domantas Sabonis had his 12th double-double of the season with 12 points and 17 rebounds. Kyle Dranginis scored 10 and Bryan Alberts made all three of his 3-point attempts for nine points. Gonzaga was 13 of 26 from long range.