Gather all ingredients. Preheat the oven to 350 degrees F (175 degrees C). Lightly oil a 9-inch square baking pan.
Heat 3 tablespoons olive oil in a large skillet over medium heat. Add chopped onion, green onions, and garlic; cook and stir until soft and lightly browned, about 5 minutes.
Stir in spinach and parsley, adding spinach in batches if it doesn't all fit in the skillet at once; cook until spinach is limp and excess liquid has evaporated, about 5 minutes. Remove from the heat; set aside to cool.
Combine feta cheese, ricotta cheese, and eggs in a large bowl until well combined; stir in spinach mixture. Lay one phyllo dough sheet in the prepared baking pan; brush lightly with olive oil. Lay another phyllo dough sheet on top; brush with olive oil. Repeat with two more phyllo dough sheets; the sheets will overlap the pan.
Spread spinach and cheese mixture into the pan. Fold any overhanging phyllo dough over filling; brush with oil.
Layer in remaining 4 phyllo dough sheets, brushing each with oil. Tuck overhanging phyllo dough into the pan to seal the filling.
Bake in the preheated oven until golden brown, 30 to 40 minutes.
Cut into squares and serve while hot.
Enjoy!
