Preheat the oven to 425°F.
In a small bowl, combine the shawarma spice mix, lemon juice, minced garlic, and olive oil.
Coat the chicken breast with the spice mixture and let it marinate for at least 15 minutes.
Chop the red bell pepper, zucchini, and red onion into bite-sized pieces. Toss with a little olive oil, salt, and pepper.
Arrange the vegetables on a baking sheet and roast in the preheated oven for about 20-25 minutes, until tender and slightly caramelized.
While the vegetables roast, heat a grill pan over medium-high heat and grill the chicken breast for about 6-7 minutes per side or until fully cooked.
Slice the grilled chicken into strips.
Assemble the bowl by placing the cooked quinoa as the base, topping with the roasted vegetables and grilled chicken.
Finish with a drizzle of tzatziki sauce over the bowl.
Serve immediately and enjoy your nutritious, flavor-packed shawarma bowl.