Toss bell peppers and onion with garlic, salt, pepper, and olive oil. Add to a sheet pan and cook for 10-12 minutes.
While onions and peppers are cooking, toss shrimp with olive oil, chili powder, cumin, onion powder and salt.
Remove onions and peppers from oven, toss and push to one side of the baking sheet. Add shrimp to the other side of the sheet and return to the oven. Cook for another 10 minutes or until shrimp are no longer translucent and cooked through.
Serve shrimp and veggies in warm tortillas with salsa, avocado and cilantro on top.