Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Ensure the frozen tilapia fillets are fully thawed and pat them very dry with paper towels to ensure a better roast.
In a large bowl, toss the broccoli florets, sliced bell peppers, and sliced zucchini with half of the olive oil, sea salt, and black pepper.
Spread the seasoned vegetables in a single layer on the prepared baking sheet and roast for 10 minutes.
Remove the pan from the oven, push the vegetables to the edges, and place the tilapia fillets in the center.
In a small ramekin, whisk together the remaining olive oil, lemon juice, minced garlic, and dried oregano.
Brush the lemon-garlic mixture generously over each tilapia fillet.
Return the pan to the oven and bake for another 10 to 12 minutes until the fish is opaque and the vegetables are tender-crisp.