Simplify the following text for a Grade 4 native English-speaking person.
Original: Oats , like rye , are usually considered a secondary crop , i.e. , derived from a weed of the primary cereal domesticates wheat and barley .
Simplified: Oats are like rye . They are normally thought as a less important crop , i.e. coming from a weed out of the main cereals wheat and barley .