The Terps' answer once the game tightened, though, might have been even better.
Midfielder Connor Kelly scored four second-half goals, including three in a row to give the Terps a four-goal lead, and their defense held off a late rally for an 8-6 victory.
The win improves No. 1 and top-seeded Maryland to 11-3 and moves it into the Big Ten championship game Saturday against Ohio State.
"The Big Ten is huge for us," Kelly said. "That was one of our goals at the beginning of the season, winning the Big Ten tournament. You've just got to focus on the little things like getting ground balls. You've just got to play some team defense and communicate."
The defending conference champion Terps, who also beat Penn State in a tournament semifinal last season, defeated the Nittany Lions, 15-11, on April 8.
A wet grass field, combined with the play of Terps goalkeeper Dan Morris and his surrounding defense, dictated a much lower scoring rematch.
The Terps made it 1-0 just 1:44 into the game on an unassisted goal by Colin Heacock (Boys' Latin) and then took a 2-0 lead with 11:50 left in the opening period on a goal by Tim Rotanz.
Maryland built a 4-1 lead by halftime as Jared Bernhardt scored with 4:33 left in the first quarter and Rotanz added his second goal with 7:37 to go in the second.
"It feels awesome," Morris said. "I think some guys had some nerves coming into semifinal, a lot of traveling. Midweek games can be challenging, but I think the guys handled it extremely well and we're all excited to get to the championship on Saturday."
Morris tied his career high with 16 saves.
Kelly scored his first goal 19 seconds into the third quarter for a 5-1 lead before Penn State scored three consecutive goals.
Morris didn't give up another goal, however, until there was 3:29 remaining in the game and his team had built an 8-4 lead.
"I felt pretty good out there," Morris said. "I thought my defense did an amazing job, and a lot of credit goes to our scout team. They gave me the looks I needed to make a save. Overall it was a good day."
Kelly now is second on the team with 32 goals behind Matt Rambo (33).
Two of Kelly's goals were unassisted, including the one he scored with 10:34 remaining that was the Terps' final score.
Mac O'Keefe and Kevin Hill scored two goals apiece for the Nittany Lions, who are ranked No. 8 nationally.
"Penn State's such a good team and I thought they played really good defense today," Terps coach John Tillman said. "They had good possessions, long possessions and made our defense work. At times we got a little antsy and we made those mistakes to make ground balls. Obviously we're fortunate [Morris] played as well as he did and our defense played as well as it did.
"It's the second time we've played on grass and the first time we've played on a wet grass field. I thought both teams weren't as clean as they normally are. I thought the grass made both teams play a little bit slower."
No. 7 Ohio State 15, No. 10 Johns Hopkins 13: Tre Leclaire scored six goals to lead the Buckeyes (13-3) over the Blue Jays (8-6) in the second Big Ten semifinal.
Shack Stanwick (Boys’ Latin) led Johns Hopkins with four goals.
Baltimore Sun staff contributed to this article.