01 - Preheat oven to 425°F. Line a rimmed baking sheet with parchment paper and set aside.
02 - Place diced eggplant, red bell pepper, and sliced red onion on the prepared baking sheet. Drizzle with 2 tablespoons olive oil and season with 1/2 teaspoon salt and 1/4 teaspoon black pepper. Toss to coat evenly and spread in a single layer. Roast for 25–30 minutes, stirring halfway through, until vegetables are golden brown and tender.
03 - While vegetables roast, rinse quinoa thoroughly under cold running water. Transfer to a medium saucepan with 2 cups water and bring to a rolling boil. Reduce heat to low, cover with a tight-fitting lid, and simmer for 15 minutes. Remove from heat and let stand, covered, for 5 minutes. Fluff grains with a fork.
04 - In a small bowl, whisk together 3 tablespoons extra-virgin olive oil, lemon juice, red wine vinegar, minced garlic, dried oregano, salt, and pepper until emulsified and well combined.
05 - In a large mixing bowl, combine the fluffy quinoa, roasted vegetables, halved cherry tomatoes, diced cucumber, and baby spinach. Drizzle dressing over the top and toss gently until everything is evenly coated.
06 - Divide the mixture among four serving bowls. Finish each bowl with a generous crumble of feta cheese, scattered fresh parsley and mint, and toasted pine nuts if desired.
07 - Serve immediately at room temperature, or refrigerate for 20–30 minutes for a refreshing chilled grain bowl.