In 10-inch nonstick skillet, cook beef and 1/4 cup of the green onions over medium-high heat, stirring occasionally, until beef is brown; drain well. Stir in barbecue sauce and frozen vegetables. Heat to boiling; reduce heat to low to keep warm.
Meanwhile, cook 1 pouch potatoes as directed on box for 4 servings, using 1 1/2 cups hot water, 1/3 cup milk and 2 tablespoons butter. Stir in remaining green onions; let stand 5 minutes.
Spoon potatoes onto center of beef mixture, leaving 2 1/2- to 3-inch rim around edge of skillet; sprinkle cheese over potatoes and beef mixture. Cover and let stand about 5 minutes or until cheese is melted. Coarsely crush chips; sprinkle around edge of skillet.