Preheat oven to 350 degrees. Mix all ingredients. Spread into greased 13x9x2 pan. Bake at 350 for 30 minutes. Cool 10 minutes and cut into squares.
2 (10-ounce) packages frozen chopped spinach, thawed and drained 1 stick butter 3 large eggs, beaten 1 teaspoon salt 1 teaspoon ground thyme garlic powder, to taste 1 cup biscuit baking mix 1 pound shredded Monterey Jack cheese