1. Peel sweet potatoes, and cut into 1/2-inch cubes. Cut yellow bell pepper into 1-inch pieces.
2. Combine sweet potatoes, bell pepper, onions, and remaining ingredients in a large zip-top plastic bag; seal bag, and turn until vegetables are evenly coated. Remove vegetable mixture from bag, and place in a single layer in a lightly greased 11- x 15-inch jelly-roll pan.
3. Bake at 450° for 30 to 35 minutes or until sweet potatoes are tender.