Two things: #1 NEVER add oatmeal (cooked or not) to meat.  That is just gross.  If I don't have any dried bread or day-old bread I want to use up, I crush some soda crackers, finely, and add them.  #2  NEVER mix beef and pork together.  Make these with straight up beef or don't bother at all.  They are really more delicious (as the recipe states) when they are covered in bread crumbs, which I do about halfway through the frying process.  If you put the bread crumbs on the raw patties before frying, the crumbs will burn and the hamburgers will not be done in the middle (unless you like halfway raw hamburger patties!). 

https://www.thespruceeats.com/basic-frikadellen-1447071

These are good served with the Swiss potato rosti recipe I posted recently.  Add to the meal some steamed green peas or green beans and you're good to go.