In a large skillet over medium-high heat, heat oil until shimmering. Add onion and cook until softened, about 5 minutes. Stir in taco seasoning, garlic, and oregano until fragrant, about 30 seconds.
Add ground turkey and cook, stirring occasionally, until almost cooked through but still slightly pink, about 2 minutes.
Stir in tomato sauce, vinegar, and brown sugar. Bring to a simmer and cook until thickened, about 4 minutes. Season to taste with salt and pepper.
Divide filling evenly among tortillas and serve with healthy garnishes such as shredded lettuce, diced tomato and avocado, scallions, and cilantro leaves.