2On a large sheet pan, toss together onion, bell peppers, zucchini, and cherry tomatoes with 2 tbsp olive oil, half the garlic, oregano, red pepper flakes, and salt. Spread in a single layer and roast for 10 minutes.
3While vegetables roast, pat shrimp dry and toss in a bowl with remaining 1 tbsp olive oil, remaining garlic, a pinch of salt, and black pepper. Zest the lemon and set zest aside; cut lemon in half.
4Remove pan from oven and push vegetables to the sides. Arrange shrimp in the center and nestle lemon halves among the vegetables. Return to oven and bake 8–10 minutes, until shrimp are pink and cooked through.
5Scatter fresh basil and lemon zest over everything. Drizzle any pan juices over the shrimp and vegetables. Serve straight from the pan.