Begin by preheating your grill or grill pan over medium-high heat.
In a small bowl, mix lemon juice, olive oil, dried oregano, dried thyme, salt, and pepper to create a marinade.
Place the chicken breast in a shallow dish and pour half of the marinade over it, ensuring it is well-coated. Let it sit for at least 15 minutes.
While the chicken marinates, toss the mixed greens with a drizzle of the remaining marinade to lightly season them.
Slice the zucchini and red bell pepper into bite-sized pieces. Place them on a baking sheet, season with a pinch of salt and pepper, and roast in a preheated oven at 400°F for 12-15 minutes until tender and slightly charred.
Grill the chicken breast for about 6-7 minutes per side or until fully cooked and the internal temperature reaches 165°F.
Once the chicken is cooked, slice it against the grain.
To serve, arrange a generous bed of mixed greens on a plate, top with the sliced chicken, and surround with the roasted vegetables. Enjoy immediately.