Preheat the grill or grill pan over medium-high heat.
In a small bowl, whisk together lemon juice, minced garlic, and a pinch of salt and pepper.
Place the chicken breast in a shallow dish and pour half of the lemon garlic marinade over it, ensuring it's well coated.
Let the chicken marinate for at least 15 minutes while you prepare the vegetables.
Preheat the oven to 425°F for roasting the vegetables.
Toss the broccoli and bell peppers in olive oil, salt, and pepper, then spread them evenly on a baking sheet.
Roast the vegetables in the oven for about 15-20 minutes until they are tender and slightly charred on the edges.
Grill the marinated chicken for about 6-7 minutes per side or until fully cooked and the internal temperature reaches 165°F.
Once the chicken is cooked, let it rest for a few minutes before slicing.
Plate the sliced chicken alongside the roasted broccoli and bell peppers, and drizzle the remaining marinade over the chicken if desired.