Presque Isle Downs also took a fourth-quarter hit in revenues, which fell 22 percent to $37 million. Slot revenues dropped $8.2 million, while table game revenues fell $1.7 million from the same period in 2011.
The company cited growing competition in Ohio for those losses.
The company said it would continue "thoughtful spending" on capital improvements this year, including hotel room renovations at Mountaineer and "redefining the gaming floors" to improve the guest experience.
Dahl said he assembled a solid team during his tenure and is confident that MTR will "continue to prosper."
Chairman Steven Billick thanked Dahl for his service and for staying on to ensure a smooth transition.
Dahl, who has more than 30 years of experience in the casino industry, was appointed to his current post in January 2011. Before that, his consulting company managed Harlow's Casino Resort in Greenville, Miss.
Dahl is also a former president and chief operating officer of Torguson Gaming Group, and former president and chief operating officer of Beau Rivage Resorts in Biloxi, Miss.
He also worked at Mississippi casinos in Gulfport and Bay St. Louis, and at The Mirage in Las Vegas.