Preheat oven to 400 degrees and grease a large baking sheet (mine was 18 x 13 - use two if necessary). For easier cleanup, you can also line with parchment paper or foil.
In a resealable small jar, combine all the ingredients for the seasonings. Seal and shake well. Reserve 1 1/2 teaspoons for the vegetables.
In a large zip-top bag, add the chicken and drizzle with 1 1/2 tablespoons olive oil and juice from 1 lime. Add 5 teaspoons of the seasonings. Seal bag and press down to allow the flavors to meld. (if prepping this ahead of time, you can also marinate the chicken in the fridge overnight)
Slice bell peppers and onions into thin strips. Spread them in an even layer on the baking sheet (do not overcrowd - use two sheet pans if necessary). Drizzle with 1 1/2 tablespoons olive oil and season with remaining seasonings. Toss to coat well.
Bake in preheated oven for 17-22 minutes (flipping chicken and tossing vegetables halfway through) or until peppers are tender and chicken is cooked through and reaches 165 F. (You can remove vegetables first if chicken is not cooked yet).
Serve with warm tortillas with sliced avocado and your favorite toppings.
To bake tortillas: wrap in aluminum foil and add to the top rack of oven while the chicken is baking for about 5 minutes.
Nutrition information does not include toppings or tortillas