Spray the inside of slow cooker with cooking spray.
Stir uncooked macaroni and vegetable oil together in the slow cooker until pasta is coated.
Stir Cheddar cheese, evaporated milk, milk, broccoli, salt, and black pepper with macaroni until fully combined.
Cover the cooker and cook on Low until macaroni is tender and the sauce is bubbling, 2 ½ to 3 hours, stirring often to reduce sticking.
