Little is known for certain about his life, and as is common for composers of the early 15th century, there are problems of identification in the existing records.
In 1423 and 1424, he may have been a vicar at St. Vincent in Soignes, a collegiate church with an active music establishment.
Antwerp Cathedral's records mention a 'Heer Jan le Grant' as a singer there from 1441 to 1443, and this may also have been him.
It is not known if he is related to Guillaume Legrant, a slightly better-known contemporary of Johannes.
The one ballade attributed to Johannes has also been suggested to be the work of Guillaume based on stylistic characteristics.