Add the steel cut oats to a 4 to 6 quart slow cooker insert that has been sprayed with non-stick cooking spray.
If you would like smaller pieces of peaches, strain the juice into the slow cooker and cut the peaches into bite sizes. Otherwise, just dump the peaches with their juice straight into the slow cooker.
Add the brown sugar, cinnamon and salt and lightly stir it into the mixture.
Slowly stir in the milk.
Cover and cook on LOW for 5 to 6 hours or overnight.
Notes
I prefer to cook my oatmeal in milk because that is just how I grew up eating it. It adds extra protein, calcium, etc. However feel free to use water if you are watching your calories. Non-dairy milks should work well in this recipe although I have not personally tested them. So feel free to experiment using almond milk, soy milk etc.