Preheat the oven to 350°F. Spray a 9×13-inch baking dish with nonstick cooking spray.

Cut the biscuits into quarters and spread them evenly across the bottom of the baking dish without pressing them together.

Brown the sausage in a skillet over medium heat until fully cooked. Drain the grease.

Spoon most of the sausage over the biscuits, leaving a small amount in the skillet for the gravy.

Bake for about 30 minutes, or until the biscuits are cooked through and lightly golden. Cover loosely with foil if needed to prevent over-browning.

Near the end of the baking time, return the skillet with the reserved sausage to medium heat and add the butter.

Once the butter melts, whisk in the flour and cook for 1–2 minutes, stirring constantly.

Stir in the garlic powder, salt, and pepper.

Slowly pour in the milk while whisking continuously until smooth.

Bring the gravy to a gentle boil, stirring constantly, until thickened. Add additional milk if needed to reach your desired consistency.

Taste and adjust the seasoning if needed.

Remove the casserole from the oven and pour the sausage gravy evenly over the top before serving.