STATE COLLEGE, Pa. (AP) -- Michigan State coach Tom Izzo said he was concerned about Wednesday night's game at Penn State -- concerned enough to give it what he calls his "Grade A prep."

The No. 5 Spartans responded with some Grade A shooting.

Morris Peterson scored 17 points and Michigan State broke open a close game by scoring the first 10 points of the second half in a 79-63 victory over Penn State.

"We came out and had a great second half," the Spartans' Mateen Cleaves said. "We got some easy baskets and that got us rolling."

The first-place Spartans (21-6, 11-2 Big Ten), who made 33-of-59 from the field, won their fourth straight and opened a one-game lead over Ohio State and Purdue in the standings. Michigan State visits Indiana on Sunday.

"We played as well as we have in the second half," Izzo said. "We didn't given them second shots and stopped turning the ball over. If Penn State would've stayed in there, I think we're in a dogfight to the end. It was critical to get off to that great start."

A.J. Granger added 15 points and Cleaves had 11 points and 10 assists. With 738 assists in his career, he moved into second place in the Big Ten record book, ahead of Michigan's Gary Grant.

Reserve David Thomas had 10 rebounds as Michigan State outrebounded the Lions 42-22.

Jarrett Stephens and Joe Crispin each scored 18 as the Lions (13-11, 5-8) lost for the fifth time in six games. The schedule doesn't get easier, with Purdue on Sunday and Ohio State next week.

"We can't allow frustration to blind us," Penn State coach Jerry Dunn said. "We've got to keep playing."

Despite shooting 57 percent in the first half, Michigan State led by only six points at halftime. Then came the onslaught. Charlie Bell opened the second half with a jumper and a fast-break layup. Peterson got a dunk on a Cleaves-led break, Andre Hutson scored inside and Peterson hit a 3-pointer. Michigan State led 52-35 and the Lions didn't threaten again.

"I got going, got some rebounds and was able to hit my shots," Peterson said. "I kept the pressure on Penn State."

Penn State missed its first three shots, turned the ball over once and had a shot blocked during the spurt -- and Dunn knew Penn State was in trouble.

They got a couple of easy baskets in transition, which we had been doing a good job of," he said. "Then they got a couple of stick-backs right away and that hurt us. You can't afford to do that against a team like this."

The Spartans went up 39-30 as Cleaves split two defenders on a fast break with 3:49 to go in the first half. But the Lions hung close. When Michigan State missed its last three shots and committed three turnovers, Penn State was within 41-35 at halftime.

Crispin had 13 points in the first half, helping Penn State stop the usual quick Spartans start by hitting his first three 3-pointers -- all off-balance with a hand in his face.

Dunn got a technical foul for running onto the court when no call was made after Crispin, driving to the basket, collided with Cleaves.