Preheat oven to 350°F. Stack tortillas, wrap in foil and bake until softened, 8 to 10 minutes.
While tortillas are baking, oil a 7-by-11-inch glass baking dish. Warm 1 Tbsp. oil in large skillet over medium-high heat. Add scallions and garlic, and cook until fragrant, about 1 minute. Stir in corn and milk and cook, stirring occasionally, until thickened, 7 to 10 minutes. Season with salt.
Remove tortillas from foil. Set aside 1/2 cup cheese. Spoon a heaping tablespoon of corn mixture in center of a tortilla. Sprinkle with a heaping tablespoon of cheese. Roll up tortilla and set in dish, seam side down. Repeat with remaining tortillas, overlapping them slightly. Pour enchilada sauce over tortillas and sprinkle with reserved 1/2 cup cheese. Bake until bubbling, about 20 minutes.