In 3-quart casserole, combine potatoes, water and butter.
Microwave at High for 10 minutes.
Add contents of seasoning packet and milk.
Stir in frozen meatballs and green beans.
Microwave at High for 16 to 23 minutes, or until potatoes are tender and sauce thickens, stirring 2 or 3 times.
Let stand, covered, for 5 minutes.