My dog ate some of my beef stew that had cooked rye grains in it — is that safe for him?

Yes, plain cooked rye in a dish like stew is safe for dogs in small amounts. The rye itself isn't toxic, but you need to consider the other ingredients in the stew, such as onions, garlic, or excessive salt, which can be harmful. As long as the portion was small and the stew didn't contain known toxins, your dog should be fine. Just offer plain food and water, and contact your vet if you notice any vomiting or unusual behavior.