Can i use regular quaker oats oatmeal to make an oatmeal bath for eczema?

Not the same: The material used in the "oatmeal bath" is not oatmeal. There is a fine powder created in the milling of many different grain products & that fine powder (an oat dust if you would) is packaged & sold as an additive for its soothing qualities. I'm suppose you could try this but would be wasting oatmeal & end up with a mess that wouldn't help much.

Needs to be finer.: For an oatmeal bath you can use unflavored instant oatmeal, quick oats, or regular slow cooking oats. Blend them at highest speed into a fine powder. You can use a blender, food processor or coffee grinder. Add ½ to 1 ½ cups to warm (not hot) water & soak for 15 to 20 minutes. Use 1/3rd cup oatmeal for babies.