Like @Brian_BSC and others, I am insulin resistant in the morning and a typical bowl of oatmeal has 27 grams of carbs before any additions. Even if I use a liberal pre-bolus time and “wait for the bend” on my CGM, the insulin just cannot keep up with the oatmeal.
As you can surmise from the many responses you’ve received, there is a range of post-oatmeal BG experience here. One option you might consider is cutting your oatmeal portion size in half and replacing it with an egg or two. That way, you still get to enjoy the taste of oatmeal and can keep the post-prandial glucose in range. If you experiment with this suggestion, try eating the egg first and then the oatmeal. I also used to add butter to oatmeal; the fat helps slow down the absorption.