Preheat grill to high heat.
Cut steak into bite-sized pieces and place in a medium-sized mixing bowl.
Pour olive oil over steak and toss until evenly coated.
In a small bowl, combine chili powder, cumin, salt, pepper, paprika, garlic powder and onion powder.
Sprinkle seasoning on top of steak and toss to coat; set aside.
Cut peppers and onion into bite-sized pieces.
Thread alternating steak, peppers, and onions onto skewers.
Grill for 8-10 minutes, turning throughout cooking, until you meat reaches desired doneness.
To make the avocado sour cream, add avocado, sour cream, minced garlic, lime juice, salt and pepper to a blender. Blend until smooth.
Serve grilled skewers with avocado sour cream, for dipping.