Add the feta cheese to a blender or food processor and blend until smooth. Transfer to a mixing bowl.
Dice the red pepper and add it along with the Gruyere to the bowl also.
Mix with a spoon until all the ingredients get thoroughly combined.
Take a piece of parchment paper and place it on your working surface. Add the ground meat mixture on top in order to form a flat and smooth 30 x 33 cm rectangle.
Add the filling on the bottom edge leaving about 2 cm space from the bottom and also the sides.
Using the parchment paper to help you hold it, start to roll towards the opposite edge. With your hands press the sides of the roll to help stick together well.
Then carefully transfer the roll along with the parchment paper and place it in the center of a 27 x 39 cm (10 x 15 inch) pan. Slowly remove the parchment paper leaving only the meatloaf in the pan. If you don't feel confident doing that, you can just cut the excess parchment paper with a pair of scissors. Leaving only a small piece on the base of the loaf which you can remove after baking.
Preheat oven to 392°F / 200°C.
In a mixing bowl add the potatoes, sweet red pepper, and 4 tablespoons of olive oil. Season with salt and pepper. Mix well to combine. Then lay the potatoes all around the meatloaf.
Add also a generous drizzle of olive oil all over the top of the meatloaf.
Toss the sprigs of thyme here and there. Pour the wine in the pan.
Bake for about 15 minutes until it gets some color. Then drop the temperature to 338°F / 170°C and bake for 35-40 minutes more. You may use an instant-read thermometer to check the internal temperature of the meat to be sure. For a moist and tender meatloaf, a temperature of 78°C is ideal. Remove from oven and let the meatloaf rest for 20 minutes. Then cut and serve!