Heat 1 tablespoon oil in a large stainless steel skillet. Add shrimp and cook 3 to 4 minutes, turning once, until cooked through. Remove to a plate and reserve.
Add remaining tablespoon oil, and peppers and onions, to the skillet. Cook for 5 minutes, stirring occasionally, scraping up any browned bits from bottom of pan. Add garlic after 4 minutes. Stir in 1/4 cup water and seasoning mix. Cook for 2 minutes, stirring occasionally. Return shrimp to skillet and heat through.
Serve with warm tortillas. If desired, accompany with sour cream, salsa, guacamole, rice and salad.