Preheat oven to 400°F. Grease a sturdy baking sheet with a tablespoon or so of oil and set aside.
In a small bowl, whisk together the cumin, chili powder, oregano, chipotle, 1 teaspoon salt, 1/2 teaspoon black pepper, lime zest, lime juice, olive oil, Worcestershire sauce, and half of the garlic until evenly combined.
In a large mixing bowl, add the ground sirloin, egg, bread crumbs, cilantro, and 3/4 of the marinade mixture from earlier. Lightly mix with your hands or a fork until evenly combined. Divide the mixture and roll into balls about the size of a golfball (or slightly smaller) and place on a plate or platter. Set aside.
In a separate bowl, toss together the onion, bell peppers, jalapeño and remaining garlic with the remaining marinade. Spread out evenly onto the prepared baking sheet and bake just until the veggies begin to soften, about 15 minutes.
Carefully remove the baking sheet from the oven and push the veggies to one side. Then lay the meatballs, in a single layer, onto the now emptied side. Return the baking sheet to the oven and bake until golden brown and fully cooked through, about 25 to 30 minutes. Serve with warmed tortillas, fresh cilantro for garnish and lime wedges. Enjoy!