Heat oven to 375 degrees F. Spray 2-1/2 to 3 quart casserole baking dish with nonstick cooking spray.*
In 12-inch skillet cook ground beef and onion until browned; drain grease. Add beans, corn, tomatoes, gravy, thyme and salt. Cook until heated through. Spoon beef mixture into casserole dish. Spread Simply Potatoes® evenly over beef mixture. Bake 30 to 35 minutes or until edges are bubbly. Remove from oven.
Heat broiler. Broil casserole 4 to 6 inches from heat, 3 to 5 minutes, until Simply Potatoes® are lightly browned.