Preheat oven to 350 degrees F (175 degrees C). Spray bottom and sides of a 9x13-inch square baking dish with cooking spray.
Melt 1/4 cup of butter in a large skillet, and cook the spinach and green onions, stirring occasionally, until the white parts of the onions are translucent, about 8 minutes. Remove from heat, and allow to cool for about 10 minutes; mix in the eggs, cottage cheese, feta cheese, and dill until thoroughly combined.
Melt remaining 3/4 cup of butter in a saucepan. Place 1 sheet of phyllo dough into the prepared baking dish, and brush with melted butter. Repeat laying down and buttering sheets until half the sheets have been used. Spread the filling over the sheets in an even layer. Place remaining phyllo sheets on the filling, buttering each sheet as before. Brush the top sheet with butter.
Bake in the preheated oven until golden brown, 45 to 50 minutes.