Rub pork with half of herbs and half of garlic. Drizzle pork and red onion slices with olive oil. Sprinkle with salt and pepper. Grill or roast at 400°F for 30 to 40 minutes or until 160°F internal temperature.
Meanwhile, cook bacon in heavy pot on medium heat. Add yellow onion and cook until translucent; add remaining garlic and cook one minute more.
Add broth and milk and bring to a simmer. Add grits and turn down heat to low; simmer 5 minutes or until liquid is absorbed, stirring occasionally. Stir in cheese and butter until melted; add remaining herbs.
Slice pork; top with red onions and serve with Cheddar grits.