Согласно Etrade, они не поддерживают заказы OCO :(
Sent: December 29, 2017 2:13 PM ET
Thank you for your message regarding the E*TRADE API.
The E*TRADE API does support placing advanced order such as OCO orders.
The E*TRADE API will return a list of all open orders including advanced order
placed on the website or E*TRADE Pro.