Preheat oven to 375ºF. Line a baking sheet with heavy-duty foil.
Warm oil in a skillet over medium-high heat. Add onion and bell pepper and cook, stirring, until softened, about 5 minutes. Stir in corn; sauté 2 minutes. Transfer to a large bowl to let cool slightly.
Add beef, bread crumbs, egg, yogurt, cilantro, chili powder, cumin, salt and pepper to bowl. Mix gently until well combined; do not overmix. Transfer to baking sheet and shape into a 12-by-4-inch loaf.
Bake until an instant-read thermometer inserted into center registers 160ºF, about 1 hour. Spread with ketchup, if desired, and let stand 10 minutes before slicing and serving.