In a large non-stick skillet, heat oil over medium heat. Add sausage and cook for 8 to 10 minutes or until browned. Add onion and red pepper to skillet; cook until softened, about 3 to 5 minutes. Toss in potatoes. Coat a 4-quart slow cooker with cooking spray; add sausage mixture to cooker.
In a large bowl beat together eggs and milk; stir in 3/4 cup of the cheese and pour over top of sausage mixture. Cover and cook on low-heat setting for 2 to 2-1/2 hours or until eggs are set and potatoes are cooked through. Remove liner from cooker. Sprinkle egg mixture with remaining cheese; let stand 10 minutes before serving.