Although 'pottage' just means soup or stew, 'English Pottage' has come to mean a clear dark meat-stock soup, though the Digby 1669 receipt includes oatmeal (British Food Trust, etc)

Original Receipt in 'The Closet Of Sir Kenelm Digby Knight, Opened ' (Digby 1669)

PLAIN SAVOURY ENGLISH POTAGE
Make it of Beef, Mutton and Veal; at last adding a Capon, or Pigeons. Put in at first a quartered Onion or two, some Oat-meal, or French barley, some bottome of a Venison-pasty-crust, twenty whole grains of Pepper: four or five Cloves at last, and a little bundle of sweet-herbs, store of Marigold-flowers. You may put in Parsley or other herbs.
Or make it with Beef, Mutton and Veal, putting in some Oat-meal, and good pot-herbs, as Parsley, Sorrel, Violet-leaves, etc. And a very little Thyme and Sweet-marjoram, scarce to be tasted: and some Marigold leaves, at last. You may begin to boil it overnight, and let it stand warm all night; then make an end of boiling it next morning. It is well to put into the pot, at first, twenty or thirty corns of whole Pepper.