Step 1Halve small potatoes; quarter larger ones. Potatoes should be roughly same size. Soften 1/2 tablespoon butter to grease 13x9-inch baking pan. Place potatoes in prepared pan. Toss with salt and pepper. Dot with remaining butter.
Step 2Bake at 375 degrees, uncovered, shaking pan occasionally to be sure potatoes don't stick, about 1 hour 15 minutes. Spread green onions over potatoes. Shake pan to mix them in. Bake until potatoes are crisp, about 30 to 40 minutes. Taste; add seasoning as desired. Serve hot with ketchup on the side.