Preheat large cast iron skillet on medium heat and swirl 1 tbsp of oil to coat. Add meat and cook for 10 minutes or until brown, breaking into small pieces with spatula. Transfer to a large slow cooker.
Return skillet to the stove and swirl another tbsp of oil to coat. Add onions and garlic; cook for 5 minutes, stirring occasionally. Transfer to a crock pot.
Return skillet to the stove and swirl last tbsp of oil to coat. Add peppers and cook for 7-10 minutes or until fragrant and browned a bit, stirring occasionally. Transfer to a slow cooker along with rice, water, tomato sauce, salt and pepper.
Stir, cover and cook on Low for 9 hours or on High for 4.5 hours (I noticed closer to a 5 hour mark casserole started to burn). Serve hot with a dollop of Greek yogurt and a toast.