Beets — Food safety facts
Safe to share · Dogs · full breakdown on the linked food page
Cooked plain beets in small cubes are safe. Oxalates mean very large amounts could irritate the kidneys, so keep it a treat.
Short answer
Yes, cooked plain beets are safe for dogs in small amounts. Offer them in small, soft cubes to prevent choking and aid digestion. While they contain oxalates, which in very large quantities could irritate the kidneys, keeping them as an occasional treat is perfectly fine. Just serve them plain without any seasoning, butter, or oil.