Tony Jones added a personal-best 185 yards receiving and a 47-yard TD, and the Wildcats (2-0) racked up 581 yards in all.
"I really think we just have a whole lot of confidence in the guys on the outside," Siemian said. "Those guys can make plays and we're just giving them chances."
It wasn't just the offense making plays.
The defense made some big ones, too, and it added up to four interceptions thrown by Syracuse's Drew Allen and one easy victory for Northwestern.
The Wildcats scored the game's first 20 points and led 34-7 at the half after collecting 387 yards, with their quarterbacks picking apart Syracuse (0-2).
They each completed 11 of 12 passes in the first half, and Colter was fine after suffering a concussion early in last week's victory at California.
He said he felt 100 percent Sunday afternoon and wound up going 15 of 18 for 116 yards while running for 87 yards in this one.
"He was really hungry to play today," said coach Pat Fitzgerald, who had an idea on Wednesday that Colter would be ready. "He kind of felt like he lost an opportunity a week ago.
"It wasn't any of his doing or our doing."
Siemian, who carried the load at quarterback last week, was 15 of 19, and Northwestern looked every bit like a team bent on showing it can beat the best of the Big Ten even though it was missing a key piece in running back Venric Mark (lower body injury).
The Wildcats have high expectations coming off a 10-win season and their first bowl victory in more than six decades. And with games against Western Michigan and Maine, they have a good chance to go to 4-0 before meeting Ohio State in the conference opener.
Syracuse, coming off a tight loss to Penn State, never had a chance in this one.
The Orange remained winless under new coach Scott Shafer and received another shaky outing from Allen. The Oklahoma transfer was 27 of 41 with 279 yards, and the Orange will now try to pick themselves up against Wagner and Tulane before beginning Atlantic Coast Conference play against Clemson.
"There were some big dudes out there on the D-line," Allen said. "They did a great job of reading me and knowing when it's going to be a quick pass and getting their hands up and batting the balls down."
Allen took "full responsibility" for this one, but the Orange's defense was every bit as brutal.
That didn't sit well with Shafer, who was promoted from defensive coordinator, and he became prickly when a student reporter asked if that group's performance was "a nightmare" for him.
"A nightmare? No. A nightmare? Hell no," he said. "It was a bad football game and a bad job of coaching by Coach Shafer. I can't wait to bounce back and try and get this thing better next week. But not a nightmare. Nightmares are for children. A childish question."
Siemian had 181 yards and threw for two touchdowns in the first half. Colter was about as good, passing for 96 and a TD while running for 67 and a score.
He led the Wildcats on a four-play, 75-yard scoring drive to start the game, finishing it with an 8-yard pass to Treyvon Green.
Jeff Budzien made it 10-0 with a 32-yard field goal with just over three minutes left in the quarter, and Northwestern struck again just over two minutes into the second, with Siemian hitting a wide open Dan Vitale on the right side for a 20-yard TD.
That made it 17-0, and the Wildcats continued to pile it on.
Traveon Henry intercepted Allen near midfield on Syracuse's next drive while falling into the Northwestern sideline, and Siemian followed with a 43-yard pass to Tony Jones over the middle to set up another field goal.
Syracuse finally scored when Jerome Smith plowed in from the 3 with 6:29 left to make it 20-7, but Northwestern answered with a 75-yard TD drive.
Colter scrambled 33 yards on a third down to keep it going and finished the possession with a 16-yard run, sticking the ball into the end zone as he got hit at the goal line by Brandon Reddish to bump the lead to 27-7 with 2:38 remaining.
Chi Chi Ariguzo then intercepted Allen with about a minute left, leading to a 5-yard strike from Siemian to Christian Jones in the right corner of the end zone with two seconds left for a 27-point halftime lead.
"We have balance right now," Fitzgerald said. "After two weeks, I'd like to think we're as balanced as anybody."