Heat olive oil in a skillet over medium-low heat.
Add the onions and sauté for 3-5 minutes, or until softened. Add the garlic, simmer for 30 seconds, then remove the pan from the heat to cool.
Place the oats in a food processor and pulse until they reach a fine texture resembling bread crumbs.
Cover a baking sheet with parchment paper.
Transfer the ground turkey to a large mixing bowl with the ground rolled oats, cooked onions and garlic, marinara, beaten egg, Worcestershire sauce, thyme, sea salt, and pepper. Mix it by hand until cohesive, and pack it into a ball.
Transfer the mixture onto the parchment-covered baking sheet and shape it into a loaf.
Place the baking sheet in the fridge for 30 minutes. This will help the loaf hold its shape.
Preheat the oven to 350ºF with the rack in the middle position.
Mix the ketchup and balsamic glaze, then brush it all over the top and sides of the meatloaf with a pastry brush.
Transfer the meatloaf to the oven and bake for about 30-40 minutes, or until the internal temperature reaches 160-165º F. (Check at the 30-minute mark to see where you're at and go from there.)
When done, remove the meatloaf from the oven. Let it sit for 10 minutes before cutting into it.