In a mixing bowl or the bowl of a stand mixer, combine the flour, salt and sugar together. (Tip: If measuring your flour in cups, without a scale, hold back 1 cup to add as needed later).
In a large measuring cup or bowl, combine the water and milk and whisk in the yeast until dissolved. Add this mixture, along with the melted butter or oil, to the dry ingredients. Mix by hand or with a dough hook, until the mixture is combined, about 2 minutes. Let the dough rest for 5 minutes.
Continue mixing the dough, adding more flour or water, as needed, until the dough becomes soft, smooth and tacky, but not sticky.
Transfer the dough to a lightly floured surface and knead for a couple of minutes, then form dough into a ball. Place the dough in a lightly oiled bowl, cover with plastic wrap and allow to sit at room temperature until doubled in size (about 60-90 minutes).
Grease one 9x5-inch loaf pans and line the a piece of parchment paper that covers the sides and extend a souple of inches over the sides. This will make it easier to get the loaf out after it's baked. Set aside.
Remove dough to a lightly floured surface and then, using a rolling pin, roll into a rectangle approximately 10 inches wide and 16 inches long.Sprinkle the dough with the 1/4 cup of brown sugar, then top with diced peaches and cinnamon. Starting on the long side, gently roll the dough jelly-roll style and pinch the seam together at the end. Also pinch the ends together.
Using a sharp knife, with the dough roll perpendicular to you, cut the roll of dough down the centre, lengthwise. Rotate each cut piece so that the cut sides are facing upward and place them side-by-side. Don't worry if some of the peaches fall out. You can replace them later. Pinch together the farthest end. Keeping the cuts sides facing upwards as much as possible, place the right-side piece over the left-side piece. Straighten it up and then repeat, pinching together the end closest to you. Gently push both ends towards the centre to shorten the braid to the length of your pan (9-inches). Using a bench scraper or spatula, carefully lift the dough into the greased loaf pan. If you had some peach pieces fall out, simply add to the top of the loaf.
Cover with a piece of plastic wrap and let rise until puffy and cresting the sides of the pan by about an inch.
Preheat oven to 350° F.
Prepare topping, by combining the oats, cinnamon and brown sugar in a small bowl. Using a fork, press the butter in to the mixture until incorporated. Sprinkle evenly over the top of the bread.
Bake in the preheated oven for 45-50 minutes total. Check after 35 minutes of baking, rotate pans front-to-back in the oven and loosely cover with a piece of aluminum foil if necessary (if bread is already well-browned), to prevent the top from over-browning. Bread should reach about 185° F. internal temperature in the centre.
Remove the bread from the oven and allow to cool in the pans for a couple of minutes. Run a sharp knife around the edge of the bread and carefully remove the loaves to a cooling rack by pulling on the parchment sides. Allow to cool for 1 hour before slicing.