Preheat and prep: Heat the oven to 400°F (200°C).
Lightly oil a 9x13-inch baking dish or similar casserole.
Build the base: In the baking dish, combine cooked lentils, chickpeas, halved tomatoes, sliced red onion, minced garlic, olives, and greens. Toss gently.
Make the seasoning mix: In a small bowl, whisk olive oil, lemon zest, lemon juice, tomato paste, vegetable broth, oregano, thyme, smoked paprika, red pepper flakes (if using), 1 teaspoon salt, and several grinds of black pepper. Whisk until smooth.
Combine: Pour the seasoning mix over the lentil-chickpea mixture.
Toss until everything is evenly coated. Taste a tomato or a leaf—adjust salt, pepper, or lemon if needed.
Add feta: Sprinkle half the feta into the mixture and fold lightly. Scatter the remaining feta on top.
Topping time: In a small bowl, mix breadcrumbs with 1 tablespoon olive oil and a pinch of salt.
Sprinkle evenly over the casserole for a golden, crunchy finish.
Bake: Place on the center rack and bake for 22–28 minutes, until the topping is golden and the tomatoes are juicy and bubbling around the edges.
Finish and rest: Let it sit for 5–10 minutes. Sprinkle with chopped parsley. Serve warm with lemon wedges, if you like.