Preheat the oven to 350 degrees F and line a cupcake pan with liners.
Melt the butter in a large skillet over medium-high heat and add the diced pepper and sausage, cook until sausage is heated through and peppers are tender.
While the sausage and peppers are cooking, whisk together eggs, milk, onion powder, and black pepper in a large bowl.
Add the cooked sausage and peppers to the egg mixture along with the cheese and mix to combine.
Use a 1/4 cup measuring cup to measure the egg mixture into the liners, there may be a little leftover, feel free to bake it up separately or discard.
Bake the quiche for 20 to 22 minutes. Remove from oven and transfer to a cooling rack. Enjoy immediately or store in the fridge or freezer.