Prepare popcorn according to package directions. Remove all unpopped kernels. Place popped corn and snack mix in 2.5-gallon resealable food storage bag.
Combine Fleischmann's, Worcestershire sauce, seasoned salt, garlic powder and onion powder in small bowl. Drizzle over popcorn mixture; close plastic bag and shake until popcorn mixture is coated evenly. Spread in 15x10-inch shallow baking pan.
Bake 10 minutes, stirring once after 5 minutes. Serve immediately or store in tightly sealed container.