In a large nonstick pan, heat 1 T olive oil and quickly sauté squash slices. Remove squash and set aside in a large bowl.
Add 1 T olive oil to pan and sauté onion 1 min. Add peppers; sauté 1 min more. Add to squash.
Add spinach, tomatoes, garlic, herbs, salt, pepper and feta to bowl with vegetables and gently mix. Taste; season if needed.
In a small bowl, mix melted butter and 6 T olive oil. Brush inside of 10” springform pan or deep pie dish with butter-oil mixture. Preheat oven to 375°.
Place a sheet of phyllo onto work surface and brush with butter-oil mixture. Place into springform pan, covering only part of the bottom and draping over the side. Rotate pan 1/8 turn and repeat with another sheet, overlapping the first. Continue with 6 more sheets, eventually covering the entire bottom and sides. Reserve 4 sheets for the top.
Place filling into phyllo-lined pan, slightly compacting it. Fold the draping phyllo on top of the filling.
Brush the top generously with butter-oil mixture. Brush reserved phyllo sheets on work surface; crumple and place them next to each other, on top of the pie.
Bake on a sheet pan 35-40 min until golden and crisp. Cool for 15 min on rack. Release the ring, garnish with chives and serve.