Place poblano chiles on a foil-lined baking sheet. Broil 8 minutes or until blackened and charred, turning after 6 minutes. Place in a paper bag; fold to close tightly. Let stand 15 minutes. Peel and discard skins. Discard seeds and stems. Chop chiles.
Coat an oval 3-quart electric slow cooker with cooking spray. Place milk and next 7 ingredients (through eggs) in slow cooker; stir with a whisk until blended. Stir in chiles, corn, and cheese. Cover and cook on LOW for 2 1/2 hours or until set. Remove lid. Cook on LOW for 15 minutes.