Sort and wash beans; place in a large Dutch oven. Cover with water 2 inches above beans; let soak overnight. Drain beans; set aside.
Brown lamb, onion, and garlic in hot oil in a large Dutch oven. Add pinto beans, bay leaf, chili powder, salt, peppercorns, and water. Bring to a boil. Reduce heat; cover and simmer for 1 1/2 hours.
Add remaining ingredients except tortillas; simmer, uncovered, 1 hour or until vegetables and lamb are tender. Remove bay leaf and peppercorns; discard. Serve stew with tortillas.
Oxmoor House Homestyle Recipes