You shouldn't be eating oats and corn anyway on Primal, or any grain.
It doesn't *have* to be grass fed beef. Just try to source the best stuff you can reasonably afford, any improvement is a good step!
It's more about eating whole, real foods. We're a one (regular) income family and a slow cooker was a good investment. I buy lots of the cheaper tough cuts and stew them for a few hours - delicious and nutritious!