In a large skillet over medium-high heat, fry the bacon for about 5-7 minutes, until crispy, flipping halfway through. Remove the bacon and place on paper towels, and set aside. Drain the bacon grease, leaving about 1 tablespoon in the pan, and add the butter. Add the shrimp, Old Bay, and half of the green onions, cooking about 3 minutes until the shrimp are cooked through. Crumble the bacon and add it to the skillet. Remove from heat and cover.
In a medium saucepan over medium-low heat, add the buttermilk and cook about 4-5 minutes until it reaches a boil. Gently stir in the grits, cover, and cook for 5-7 minutes. Remove the grits from the heat and stir in cheese.
Serve shrimp and bacon over grits.