In a medium pan over medium heat, warm oil and add ground sausage. Cook for 5-7 minutes, breaking the sausage as you go until it has been browned on all sides and cooked through. Drain excess grease.
In a large bowl, add all ingredients together except for half of each cheese.
Insert liner in slow cooker or grease the inside, then pour in the mixed ingredients.
Top with remaining cheeses.
Cover with lid and cook on high for 1 ½-2 hours or low for 3-4 hours.
Notes
Notes: You can top the cheese with pepperoni or cooked crumbled bacon, if desired.