Chili Cheese Popcorn

8 cups popped popcorn
2 tablespoons margarine
1/4 teaspoon chili powder
1/4 teaspoon garlic salt
1/4 cup grated American cheese

Melt the butter in a small saucepan. Remove from heat. Add chili powder and garlic salt. Stir to mix well. Toss with hot popcorn. Add cheese and toss. Add salt, if desired. Serve hot or at room temperature.