Heat oven to 400 degrees. Spray a 10-inch pie plate with non-stick spray, and set aside.
Wilt spinach in a non-stick skillet for 3-5 minutes, adding 1 tablespoon water to keep it from sticking to pan, or blanch spinach in boiling water 1-2 minutes, until just cooked. Drain well in colander and squeeze out excess water.
Arrange spinach evenly in prepared pie plate. Arrange cheese and chopped onions over spinach. Stir together milk and eggs, and then stir in parsley, dill, salt and black pepper. Stir in baking mix, until combined. Pour over ingredients in pie plate.
Bake 30 minutes, or until knife inserted in center comes out clean. Let stand 5 minutes before serving.