BOSTON -- Who knew the only thing Colton Cowser needed to tap into his power was a little friendly competition via the arrival of his good friend Jackson Holliday?

“As soon as Jackson got called up, I was messing around and I was like, ‘If Jackson hits a home run before me, I’m going to be pretty upset,’” Cowser said.

Holliday (MLB Pipeline’s No. 1 overall prospect) played his first two big league games this week at Fenway Park, but it was Cowser who stole the show. The 24-year-old outfielder slugged the first two home runs of his MLB career in the Orioles’ 9-4, 10-inning win over the Red Sox on Thursday night, capping a huge series for the 2021 first-round Draft pick.

Cowser continued a torrid start to his 2024 rookie season with a historic breakout in Boston. He became the first player in franchise history to record 10 RBIs in a three-game series at Fenway -- he drove in four on Tuesday, two on Wednesday and four more on Thursday -- while going 6-for-13 with five extra-base hits in the O’s sweep.

As American League East rivals, the Orioles and Red Sox play multiple series every year in Boston. Yet, Cowser’s feat stands alone.

“He’s just scratching the surface,” said shortstop Gunnar Henderson, who hit the go-ahead two-run homer in the six-run 10th inning.

It was a momentous day for Cowser, even before Thursday’s game began.

Prior to the contest, Cowser and Holliday went inside the fabled Green Monster in left field and left their mark on its historic 112-year-old walls. Per tradition, both placed their signatures there -- with Cowser making sure to find a rare high spot that had been previously untouched.

“It’s a really cool ballpark,” Cowser said. “It’s one of those ones as a kid you grow up you’re like, ‘Oh, I just want to visit it,’ let alone play in it. It’s a blessing.”

Now, Cowser can say he’s hit a home run on top of the Monster, too.

In the fifth, Cowser swatted an opposite-field solo shot off Red Sox starter Garrett Whitlock that clanged off the high left-field seats before bouncing back onto the field. The milestone homer came in his 37th big league game and his 82nd at-bat.

“I was trying to keep it under 100 at-bats,” Cowser said with a smirk.

Cowser’s second MLB home run was a no-doubter. He jumped on a 3-0 pitch from right-hander Isaiah Campbell and jolted it a Statcast-projected 438 feet over Baltimore’s bullpen in right field. It pushed the Orioles’ lead to 9-3, putting the game out of reach.

“That was a ‘Wow’ moment there with the 3-0 when he goes into David Ortiz land,” manager Brandon Hyde said. “That was an impressive swing. Awesome to see him go opposite-field homer, too. He did a lot of great things this series.”

The O’s were confident that Cowser’s 26-game debut stint last year -- in which he went 7-for-61 (.115) with a .434 OPS -- wasn’t indicative of the type of player he could become. Cowser came into Spring Training motivated to prove that, had a huge spring and then broke camp with the team, making his first career Opening Day roster.

Since then, Cowser hasn’t slowed down. Through 11 games, he is 11-for-24 (.458) with five doubles, two homers, 11 RBIs and a 1.379 OPS.

“He’s been a lot of fun to watch,” right-hander Grayson Rodriguez said. “I think he’s really starting to come alive, showing everybody the player that he is and the special talent that he is as well.”

After making only two starts over Baltimore’s first eight games, Cowser has forced his way into being a regular in the lineup, where he began all three games in Boston.

However, Cowser insists the increase in playing time -- along with the big week stats-wise -- hasn’t necessarily brought a confidence boost.

“It doesn’t change much,” Cowser said. “This year, I was trying to be a little bit more confident, regardless of what happens. Whether I go 0-for-4 or 4-for-4, I want to forget about it that night and then go into the next day with the same mentality. Really not change my process or change how I go about my business.”

So far, that’s going quite well. And Cowser is sure that Holliday (hitless over his first eight at-bats) will join him in the friendly homer competition soon enough.

“I know his is coming soon,” Cowser said.