Preheat your oven to 400°F (200°C) and line a large sheet pan with parchment paper for easy cleanup.
Cut the chicken breast into 1-inch bite-sized pieces and halve the baby potatoes to ensure even cooking.
Chop the broccoli into florets, slice the zucchini into half-moons, and dice the red bell pepper into large chunks.
In a small bowl, whisk together the olive oil, lemon juice, minced garlic, dried oregano, sea salt, and black pepper.
Place the chicken and all vegetables on the prepared sheet pan, then drizzle the lemon-herb marinade over everything.
Toss thoroughly with your hands or tongs to ensure every piece is well-coated, then spread into a single layer.
Roast for 20-25 minutes, tossing halfway through, until the chicken is cooked through and the potatoes are fork-tender.
Serve immediately or portion into containers for a high-protein meal prep that stays fresh all week.