Preheat an oven to 375 degrees F (190 degrees C). Lightly grease a 9x13 inch baking dish.
Heat the olive oil in a saucepan over medium heat. Stir in the onion, and cook until the onion softens and turns translucent, about 5 minutes. Pour in the chicken broth and milk. Bring to a boil over high heat, then turn the heat to low. Slowly whisk in the grits, then cover the saucepan, and cook for 5 minutes.
Once the grits have cooked, stir in the salt, pepper, cumin, chipotle peppers, green chiles, and 1 cup of Cheddar cheese until the cheese has melted. Pour the grits into the prepared 9x13 inch dish, and sprinkle with the remaining 1/2 cup of Cheddar cheese.
Bake in the preheated oven until the cheese is bubbly, and has begun to brown, 30-45 minutes.