In a large bowl, combine potatoes, red peppers and onions. In a small bowl, mix oil, garlic, salt and pepper; add to potato mixture and toss to coat.
Transfer to two 13x9-in. disposable foil pans; cover with foil. Place pans on grill rack over medium heat; cook, covered, 30-35 minutes or until potatoes are tender. Remove from heat.
Grill hot dogs, covered, over medium heat 7-9 minutes or until heated through, turning occasionally. Place buns on grill, cut side down; grill until lightly toasted. Place hot dogs and potato mixture in buns. Serve with remaining potato mixture.