Jeffries is the happy winner of $6,000 after the rookie - only recently called back up to the Big Leagues - as part of Maryland Lottery's FAST PLAY Home Run Riches Bases Loaded second-chance promotion.
He is the sixth to cash in on an Orioles grand slam.
In his return to MLB after being sent down to AAA earlier this season, Jackson mashed an 0-2 hanging breaking ball that Toronto's Yerry Rodriguez left over the plate into the upper deck in right field.
It marked his first career home run in the Big Leagues, and he did it in a big way. It was also a happy Holliday for Jeffries, who won big on the promotion.
The Lottery selects one Contestant of the Game for each of the Orioles 162 regular-season games. They receive $500 simply for being chosen, and $500 for any home run the O's hit in their designated game; however, if that homer comes with the bases full, the winner gets a $5,000 bonus.
Jeffries said he was at home watching the July 31 game against the Toronto Blue Jays when the Orioles started making things interesting in the fifth inning as they had runners on first and second.
Infielder Jordan Westburg then set the table for Holliday's big hit after he was struck to load the bases.
“I told my wife. I need a single, a walk, an infield hit. Anything to get the bases loaded,” Jeffries mused. "When he hit it to Eutaw Street, I jumped up and down a little bit.
"It was kinda cool ... they don't hit grand slams every day."
Want breaking news in the DMV as it happens, or want to contribute? Join the DMV All Incidents Facebook group.
Click here to follow Daily Voice Glenwood-Glenelg and receive free news updates.