1. Combine first 6 ingredients in a large zip-top plastic bag. Add 1 1/2 teaspoons oil and chicken; seal. Marinate in refrigerator 2 hours, turning bag occasionally.
2. Preheat grill to medium-high heat.
3. Cut potatoes in half lengthwise; cut each potato piece in half crosswise. Add potato wedges to a large pot of boiling water; reduce heat, and simmer 5 minutes. Drain. Combine potatoes, 1 1/2 teaspoons oil, and 1/4 teaspoon salt.
4. Remove chicken from marinade; discard marinade. Sprinkle chicken with 1/4 teaspoon salt and black pepper. Arrange on a grill rack coated with cooking spray; grill 8 minutes on each side or until done. Remove from grill; keep warm. (Discard skin before serving.) Arrange potato on grill rack; grill 4 minutes on each side or until done.
5. Heat remaining 1 tablespoon oil in a large skillet over high heat. Add yellow onion; stir-fry 1 minute. Add bell peppers; stir-fry 2 minutes. Add tomato sauce and vinegar; cook 1 minute, stirring constantly. Serve bell pepper mixture with chicken and potatoes. Top with green onions.
Wine note: Aussie-style Marinated Chicken Thighs with Sweet Potato include honey and five-spice, flavors that are often apparent in viognier wines. Australia's Yalumba makes several versions of this aromatic white, including Yalumba Eden Valley 2008 ($19), with exotic spice, supple apricot, and lemon curd flavors. A substantial, almost viscous, body allows this wine to linger on the palate with even the most flavorful foods. --Jeffery Lindenmuth