Mix together fajita seasonings in a bowl - garlic, cumin, chili powder, smoked paprika, onion powder, brown sugar and salt.
Mix half of fajita seasonings with orange juice and 2 tablespoons olive oil.
Pour marinade into a ziploc bag or shallow dish and add chicken, turning to coat both sides.
Cover and refrigerate until ready to grill.
Thinly slice peppers and onions.
Mix with 1/4 cup olive oil and remaining fajita seasonings.
Prepare grill to 300°.
Add chicken to the grill over indirect heat with vegetables on a grill pan. Close the lid and cook 10 minutes.
Turn chicken and stir the vegetables. Close the grill and continue to cook until chicken reaches 165° internally, about 15 to 20 minutes.
Remove from grill and allow chicken to rest 5 minutes before slicing.
Mix dressing by whisking mayonnaise, milk, salsa, cumin and ranch dressing mix together.
Tear lettuce into bite size pieces, slice tomatoes, chop cilantro and shred cheese.
Build salads by layering lettuce, chicken, peppers, onions, tomatoes, cilantro and cheese.
Drizzle with dressing.