Stevens and Watkins combined for 27 points and made 11 of 12 field-goal attempts in the first half, when the Nittany Lions (12-5, 2-2 Big Ten) opened a 16-point lead and never trailed.

Bryant McIntosh had 18 points and Scottie Lindsey had nine points for the Wildcats (10-7, 1-3), who lost their second straight.

The 6-foot-8 Stevens made 14 of 19 shots, and the Nittany Lions dominated inside with 48 points in the paint. The 6-foot-9, 254-pound Watkins has five double-doubles in his past seven games.

Tony Carr had 12 points, five assists and four rebounds for the Nittany Lions, who play at Indiana on Tuesday.

Helped by their interior presence, Penn State shot 54.5 percent from the field and had a 40-27 rebounding edge. Stevens had five rebounds.

The Wildcats, more reliant on perimeter scoring, shot 37.1 percent from the field, including 11-of-28 from three-point range.

Vic Law had eight points, six rebounds and five assists for Northwestern. Lindsey, Northwestern's leading scorer with a 14.6 average, was 3 of 17 from the field.

Stevens had seven points and Watkins had five when Penn State jumped to a 19-8 lead, and the Nittany Lions kept coming.

Stevens had a 3-pointer, a dunk and a jumper in the next five minutes to help the Lions to a 31-15 lead with 7:44 remaining in the half.

McIntosh had five points and Gavin Skelly and Lindsey hit 3-pointers as the Wildcats closed the half on a 19-10 run to get within 41-34.

Threes by McIntosh and Jordan Ash in the first five minutes of the second half closed the gap even further at 47-44, but Penn State ran off nine straight points -- all in the paint -- for a 56-44 lead.

--Field Level Media