Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper or lightly grease it.
In a large mixing bowl, combine the ground breakfast sausage, biscuit baking mix, shredded cheddar cheese, and fresh blueberries.
In a separate small bowl, whisk together the milk and egg until well combined.
Pour the milk and egg mixture into the sausage mixture.
Using your hands or a spoon, mix all ingredients together until just combined, being careful not to crush the blueberries too much.
Form the mixture into 1-inch diameter balls and place them evenly spaced on the prepared baking sheet.
Bake in the preheated oven for 20 to 25 minutes, or until the sausage balls are cooked through and golden brown on the outside.
Remove from the oven and allow to cool slightly before serving.