Preheat oven to 350 degrees.
Brush a 9 x 5-inch loaf pan with oil or spray with cooking spray. Set aside until needed.
Combine the apples with lemon juice in a small bowl. Set aside until needed.
Heat the olive oil and butter in a large skillet or saute pan over medium-high heat. Add the onion, reduce the heat to medium, and cook for 7-8 minutes or until beginning to soften.
Add the apples and any accumulated juices and cook for 3-4 minutes, or until they begin to soften. Stir in the sage. Remove from the heat, transfer to a large bowl, and let cool at least 10 minutes.
Add the parsley, oats, egg, milk, salt and freshly ground black pepper and mix well.
Add the ground turkey and mix until everything is evenly incorporated. After mixing, let it sit for 5 minutes to allow the oats to hydrate properly. (This helps the meatloaf hold together and stay moist.)
Place in the prepared loaf pan and smooth the top into a nice loaf shape.
Bake for 50–60 minutes or until a thermometer inserted into the center registers 165 degrees.
While the meatloaf bakes, prepare the glaze. Heat olive oil in a small saucepan over medium heat. Add the garlic and cook 30 seconds or until fragrant. Remove from the heat to add the remaining ingredients to keep the garlic from scorching and the liquid ingredients from spattering.
Add remaining ingredients, return to the heat, and bring to a simmer. Cook for 1-2 minutes to combine flavors and heat through.
During the last 10–15 minutes of baking, brush some of the glaze onto the meatloaf, then return it to the oven to finish baking and set.
Let rest 10 minutes before slicing. Serve with the remaining glaze.