The plates in an Oster waffle maker cannot be removed. If they become dirty or have caked-on food, they can be cleaned while still attached to the machine. If they are irreparably damaged, the machine needs to be replaced.
Taking care of the Oster waffle maker is the best way to prevent needing to change the cooking plates. This can be done by cleaning it properly. When cleaning, never submerge the unit under water. Instead, wash the plates with a soapy cloth or sponge while they are still attached to the machine, then wipe them clean with a hot cloth or sponge. Always use hot water, as this allows the machine to dry faster.
If there is caked-on food, use a non-abrasive cleanser or a nylon scrub pad. Do not use steel wool or abrasive cleaners, as these can damage the non-stick surface of the Oster waffle iron and reduce the lifespan of the machine. When the machine is clean and not in use, it should be stored safely in a clean, dry environment away from children and pets.
Replacement of any parts, including the plates, should only be done by an authorized professional, otherwise there is a risk of irreparable damage to the machine and electrocution.