Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
In a large bowl, toss the broccoli florets, bell pepper strips, and cherry tomatoes with 1 tablespoon of olive oil, half the sea salt, and half the black pepper.
Spread the vegetables in a single layer on the prepared baking sheet and roast for 10 minutes.
While the vegetables roast, mince the garlic and whisk it in a small bowl with the remaining olive oil, lemon juice, dried oregano, and the rest of the salt and pepper.
Pat the cod fillet dry with a paper towel and brush the lemon-garlic mixture generously over the top and sides of the fish.
Remove the baking sheet from the oven, push the vegetables to the edges, and place the cod fillet in the center.
Return the pan to the oven and bake for an additional 10 to 12 minutes, or until the fish is opaque and flakes easily with a fork.