Line a 5- to 6-quart slow cooker with a Reynolds Kitchen Slow Cooker Liner. Fit liner snugly against the bottom and sides of the bowl; pull top of liner over the rim. Set aside.
Cook and stir ground beef, bell peppers, and onions in a large skillet over medium-high heat, stirring occasionally, until beef is browned and crumbly. Drain grease.
Spoon beef mixture into the lined slow cooker. Add beans, tomato sauce, diced tomatoes and green chiles, and seasoning mix to beef mixture; stir gently with a wooden or plastic spoon.
Cover and cook until hot and bubbly throughout, Low for 6 to 7 hours or High for 3 to 3 1/2 hours.
Carefully remove the lid to allow steam to escape. Stir gently, then top with cheese and dollops of sour cream. Serve chili directly from the slow cooker liner.