Prosecutors said that Mirza he had researched targets to attack including Birmingham's Central Synagogue and the city's RAF careers office.
He practiced the best way to kill someone using a martial arts dummy at home and came up with a way to hide the knife.
Police were alerted to the couple thanks to intelligence from M15.
Taheer was arrested a week after the Westminster Bridge terror attack in London.
The jury took less than a day to convict his wife Taheer and Mirza’s sister Zainab Mirza, also pleaded guilty to sending him terrorist material.
All three will be sentenced next week.