1Heat gas or charcoal grill. Cut 4 (20x18-inch) sheets of heavy-duty foil. In large bowl, mix beef, bell peppers, onion, seasoning mix and water.
2Place 1/4 of beef mixture on center of each foil sheet. Bring up 2 sides of foil over beef mixture so edges meet. Seal edges, making tight 1/2-inch fold; fold again, allowing space for heat circulation and expansion. Fold other sides to seal.
3Place packets on grill over low heat. Cover grill; cook 13 to 18 minutes, rotating packets 1/2 turn after about 6 minutes, until beef is cooked to desired doneness and peppers are tender.
4To serve, cut large X across top of each packet; carefully fold back foil to allow steam to escape. Serve beef mixture with tortillas, salsa and sour cream.