Heat oven to 425°F. Spray 13x9-inch (3-quart) glass baking dish with nonstick cooking spray. Place sausage and bell peppers in sprayed baking dish. Pierce sausage several times with fork.
In small saucepan, combine jelly and mustard. Heat over low heat until melted, stirring frequently. Brush half of jelly mixture over sausage and bell peppers.
Bake at 425°F. for 10 minutes.
Remove baking dish from oven. Add apples to baking dish. Brush remaining jelly mixture over sausage, bell peppers and apples.
Return to oven; bake an additional 10 minutes or until thoroughly heated. Cut sausage before serving.