Press thawed potatoes between paper towel to remove moisture; set aside.
In a 10-inch ovenproof skillet, combine apple, onion, water, and sage; bring to boiling; reduce heat; cook uncovered, over medium-high heat until onion is tender; remove from heat.
Stir in potatoes and ham.
In medium bowl, combine milk, eggs, cheese and salt; pour into skillet over potato mixture; do not stir.
Bake, uncovered, in a 350°F oven for 30-35 minutes or just until center appears set.