Mix yeast, sugar, coarse salt, oil, and water in a bowl. For example, in a mixer.
Add the oatmeal, durum flour, and finally the all-purpose flour little by little - until the dough is smooth and elastic.
Let the dough rise for 30 minutes under shower caps or a cloth.
Spread the dough out on a floured surface into a large rectangle.
Fold the ends towards the middle and press the folds together.
Roll the dough into a log, rolling from the top down.
Place the dough in a lined baking form, seam side down.
Let the bread rise for 30 minutes.
Score the bread and sprinkle it generously with flour, so the crust becomes crispy and doesn't burn.
Baking time: 10 minutes at 250 degrees Celsius (482 degrees Fahrenheit) with fan + 20 minutes at 200 degrees Celsius (392 degrees Fahrenheit) with fan.