Preheat oven to 375°F. Spray a 12-cup muffin pan with cooking spray.Heat the olive oil in a medium skillet over medium heat and add the bell pepper and chicken sausage. Cook 5-6 minutes until the peppers start to soften and the sausage is browned. Stir in â…“ cup of scallions. Remove from heat.Whisk the oats, flour, baking powder, salt, garlic powder, and thyme together in a large mixing bowl. Stir in the sausage mixture from the pan and all of the cheese except for 2 tablespoons (which will be used for the topping).Whisk the eggs, milk, and butter together in another bowl. Pour the wet ingredients into the dry ingredients and stir until just combined.Spoon the batter into the muffin pan, making 12 muffins. Sprinkle the tops with some sliced scallions and cheese. Bake in the center of the oven for 16-18 minutes, until the muffins are puffed up and cooked through. Remove from oven and cool on a wire rack for 10 minutes before serving.