Place apples in a lightly greased 6-quart slow cooker; drizzle with lemon juice, and toss to coat.
Combine flour and next 3 ingredients in a medium bowl. Cut butter into flour mixture with a pastry blender or two forks until mixture resembles coarse meal; sprinkle over apples.
Cover and cook on HIGH 3 hours or until apples are tender. Sprinkle with pecans. Serve warm with ice cream.