Place shrimp in a 1-gallon zip-loc bag; place bag in bowl and set aside.
For marinade, in a small bowl, combine onion, oil, sugar, cayenne pepper, salt, oregano and garlic powder; pour marinade over shimp.
Marinate shrimp 3 hours in refrigerator, turning occasionally.
Cut bacon slices into halves lenghtwise, then crosswise. To prevent flare ups, pre-cook bacon in microwave for 1 minute.
Drain shrimp; reserve marinade. Wrap bacon strips around shrimp and slide on to skewer.
Grill shrimp on uncovered grill over medium-hot heat for 6 minutes or until bacon and shrimp are done, turning once and basting with marinade.