In a large pot, bring salted water to a boil. Add the penne pasta and cook according to package instructions until al dente. Drain and set aside.
In a large skillet, heat olive oil over medium heat. Add the diced zucchini, eggplant, bell pepper, and chopped red onion. Sauté for about 5-7 minutes, until the vegetables begin to soften.
Add the minced garlic and cook for an additional minute until fragrant.
Stir in the diced tomatoes, spinach, oregano, basil, salt, and pepper. Allow the mixture to simmer for 5 minutes, until the spinach wilts and the flavors meld together.
In a large bowl, combine the cooked pasta, sautéed vegetable mixture, and ricotta cheese. Mix well until everything is evenly coated.
Transfer the pasta mixture to a greased baking dish. Sprinkle the crumbled feta and shredded mozzarella cheese on top.
Cover the dish with aluminum foil and bake in the preheated oven for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and let it rest for a few minutes before serving. Garnish with fresh basil leaves.
Notes
Serve the pasta bake directly from the dish with a side salad. Drizzle with extra olive oil and a sprinkle of fresh herbs for added color and flavor.