Heat gas or charcoal grill. In 1-quart saucepan, mix corn, bell pepper, vinegar, chili powder and cumin. Heat to boiling. Reduce heat to medium-low. Cook about 5 minutes or until vegetables are crisp-tender.
Cover and grill burgers over medium heat 8 to 12 minutes, turning once, until heated through.
Cut burgers in half. Place each burger half in pita bread pocket. Top with corn mixture and sour cream.