Preheat oven to 375°F. Grease a 12-cup muffin pan with oil.
Cook sausage in a skillet over medium heat, 6–8 minutes, breaking it up. Drain and let cool slightly.
Whisk milk, beaten eggs, and melted butter in a large bowl.
Stir in baking mix, garlic powder, onion powder, salt, and pepper until just combined.
Fold in cooked sausage, shredded cheddar, and green onions until evenly distributed.
Divide batter among muffin cups, filling each about three-quarters full.
Bake 18–22 minutes until golden and a toothpick comes out clean.
Cool 5 minutes in the pan, then transfer muffins to a rack to finish cooling.