Preheat oven to 350°F.
Put butter in 8" x 8" baking pan and melt it in oven (careful not to burn). Remove from oven and set aside.
In a large bowl, combine eggs, salt, baking powder, green chiles, cheeses and the melted butter. Mix well.
Pour mixture into the baking pan. Bake for 30-35 minutes or until egg is cooked in center and casserole is light brown.
Cut into 1-inch squares and serve warm or at room temperature.
Can be frozen, once cooked, and reheated.