Markakis, who batted second and started in right field, was 2-for-3 with three runs scored and four RBIs.
He struck out looking against Akron knuckleballer Steven Wright, then hit a 3-0 pitch from Wright in his second at-bat for a two-run home run in the third inning. In the seventh, he hit a two-run homer off reliever Tyler Sturdevant.
Showalter said Markakis will play at Bowie through Monday and he hopes to have the Gold Glove right fielder back for Thursday's workout and ready to play Friday.
Catcher Taylor Teagarden (back) is also on a rehab assignment with Bowie. He went 1-for-2 with two walks and a run scored as the team's designated hitter. He will catch tomorrow for the Baysox.
"It depends on what their needs are," Showalter said. "If they need more at bats, we can get it done in Delmarva or Aberdeen [while Bowie is on break]. I'm hoping everything goes well with Nicky and he can join us for the workout on Thursday."
Outfielder Endy Chavez (hamstring) is slightly behind Markakis and Teagarden, but could return early in the second half. He is slated to play in the Gulf Coast League on Tuesday and Wednesday, then be re-evaluated.