Preheat oven to 375°F.

Using a large bowl, add thawed spinach. Use paper towels to press out as much liquid out as possible; set spinach aside.

Using a large skillet, add 2 Tbsp of olive oil and place over medium heat. Once hot, add yellow onions and garlic. Sauté for 4-5 minutes, or until onions begin to soften. Transfer onions and garlic into bowl with the spinach.

Add remaining filling ingredients (green onions, feta, parsley, dill, oregano, eggs, lemon juice and pepper); stir until well combined.

Unroll phyllo dough and cover with lightly damp towel to prevent it from drying out.

Grease a 9”x13” baking dish. Place 2 sheets of phyllo dough into bottom and sides of dish. Brush dough with some of the remaining olive oil. Place 2 more sheets of phyllo dough into pan and brush with more olive oil. Repeat process 3 more times, or until you have used 10 total sheets of phyllo dough.

Spread the spinach filling mixture evenly over phyllo dough. Fold the edges of the phyllo dough down over the filling. Continue adding 2 sheets of phyllo dough and brushing with olive oil until all phyllo dough has been used. Brush top of phyllo dough with remaining olive oil.

Before baking, use a sharp knife to cut the spanakopita into 2½-3" squares. (Note: Preslicing will make it easier to remove from pan once baked.)

Bake at 375°F for 40-45 minutes, or until top is golden and crispy to the touch.