Ever since 1.11 came out I have not been able to summon horses. I have always used the same code and it used to work fine in 1.10. Here is the code I used: /summon EntityHorse ~0 ~1 ~0 {Attributes:[

{Name:generic.maxHealth,Base:60.000}

,

{Name:generic.movementSpeed,Base:0.3375}

,

{Name:horse.jumpStrength,Base:1.0}

],Type:0,Tame:1,SaddleItem:{id:329}}