CHICAGO — In a span of two pitches, the Washington Nationals turned what could’ve been a tight loss into an uplifting win.

Bryce Harper and company are one dangerous bunch on the road.

Matt Wieters hit a tiebreaking grand slam off Carl Edwards Jr. in Washington’s five-run eighth inning, helping the Nationals beat the Chicago Cubs 9-4 on Sunday.

“We’re kind of a MASH unit out there but everybody is contributing,” Washington manager Dusty Baker said. “That helps a lot when you can take two out of three without your top starters. ... That was a big game for us to win.”

Harper started the go-ahead rally with a one-out infield single against Mike Montgomery. Ryan Zimmerman doubled against Edwards (3-3) and Daniel Murphy was walked intentionally to load the bases.

Edwards’ next pitch hit Anthony Rendon, tying it at 4, and Wieters followed with a drive over the wall in center for his third career grand slam.

“It was a first-pitch breaking ball, but out of his hands I recognized it up and it was something that I felt like I could get in the air and it just happened to carry it out,” Wieters said.

Edwards (3-3) has allowed at least one run in each of his last three appearances.

“We just got to get him back to being normal because he’s a really big part of our success,” manager Joe Maddon said.

Wieters tied a career high with five RBIs and Rendon also had a run-scoring double for NL East-leading Washington, which improved to 36-22 on the road. Brian Goodwin homered, drove in two runs and robbed Jon Jay of a hit with a terrific diving catch.

The Nationals (65-44) faced the Cubs without their three best starting pitchers. Max Scherzer was pushed back after he left his previous start with neck spasms. Gio Gonzalez is on the paternity list, and Stephen Strasburg is on the 10-day disabled list with a right elbow injury.