Preheat oven to 425 degrees Fahrenheit. Line a large baking sheet with parchment paper.

In a medium saucepan, combine quinoa and vegetable broth. Bring to a boil, then reduce heat to low, cover, and simmer for 15 minutes until liquid is absorbed. Remove from heat and let stand covered for 5 minutes, then fluff with a fork.

Toss the red bell pepper, zucchini, red onion, and cherry tomatoes with 2 tablespoons olive oil, oregano, salt, and pepper on the prepared baking sheet. Spread in a single layer.

Roast vegetables in preheated oven for 25-30 minutes, stirring halfway through, until vegetables are tender and lightly caramelized at the edges.

Transfer cooked quinoa to a large serving bowl. Add roasted vegetables and gently toss to combine.

Drizzle with remaining 1 tablespoon olive oil and lemon juice. Add crumbled feta cheese and fresh parsley. Toss gently to combine.

Taste and adjust seasoning with additional salt and pepper if needed. Serve warm or at room temperature.