In a medium-sized bowl, mix together the oregano, paprika, sugar, cayenne, cumin, salt and pepper. Add the garlic, oil and vinegar. Set aside until ready to use. This mixture will last one week in the refrigerator.
Coat the chicken with the mixture and let it sit at room temp for about 1 hour before grilling (this is enough marinating time or you can do longer). Grill the chicken for about 5 minutes on the first side, flip and then repeat on the second side (or until the internal temperature of each chicken breast is 150˚F).