Spread chicken, peppers and onions on a baking sheet sprayed with some cooking spray, drizzle with olive oil and season with salt and pepper.
In a small bowl, combine chili powder, cumin, paprika, garlic powder and oregano. Sprinkle the spices evenly over the chicken and peppers, tossing to coat and spread out in a single layer on the baking sheet.
Bake in the oven for about 20 to 25 minutes, tossing halfway through, and continue cooking until veggies are tender and chicken is cooked through. (if you want some char on your veggies, remove chicken from baking sheet and pop veggies under the broiler for about 3 to 5 minutes until the edges start to char slightly.)
Drizzle with lime juice and sprinkle with fresh cilantro. Serve with lettuce cups or tortillas and desired toppings. Enjoy!