Heat 1 tablespoon of the oil in a large nonstick skillet over medium-high heat. Add beef to skillet and cook, stirring occasionally, for 8 minutes, draining any accumulated fat. Remove beef to slow cooker; reduce heat to medium. Add 1 teaspoon oil to skillet; add garlic and onion and cook, stirring, for 2 minutes. Stir in 3 tablespoons chili powder, 2 teaspoons cumin, 1/2 teaspoon salt and 1/4 teaspoon cayenne; cook 1 minute, stirring constantly.