Preheat the oven to 350°F. Line a muffin pan with paper liners or grease lightly.
In a large skillet over medium-high heat, cook sausage until browned. Remove sausage from the pan, leaving a little grease behind.
Chop the bell pepper and roughly chop the spinach.
Sauté the bell pepper and spinach in the same skillet until softened, about 3–4 minutes.
In a large mixing bowl, whisk together the sausage, eggs, milk, Bisquick, salt, pepper, garlic powder, and onion powder.
Fold in the sautéed vegetables and cheddar cheese.
Scoop the mixture evenly into the prepared muffin pan, filling each cup full.
Bake for 18–20 minutes, or until muffins are set and golden on top.
Remove from the oven and let cool in the pan for 5 minutes before transferring to a cooling rack.
Garnish with fresh parsley before serving.