In a large bowl, combine the ground turkey, egg, oats, onion, bell pepper, garlic, salt, pepper, oregano, and paprika.
Mix gently with your hands until just combined, being careful not to overwork the meat.
Shape the mixture into a compact loaf that fits comfortably inside your slow cooker.
Place a piece of parchment paper at the bottom of the slow cooker to prevent sticking and lift the loaf out easily later.
In a small bowl, whisk together the tomato paste, maple syrup, and apple cider vinegar to create the glaze.
Brush half of the glaze over the top of the turkey loaf.
Cover and cook on low for 5 to 6 hours or on high for 2.5 to 3 hours until the internal temperature reaches 165°F.
Brush the remaining glaze over the loaf during the last 30 minutes of cooking for a glossy finish.