OCO order

What it is

OCO stands for One-Cancels-Other. It's a paired order where two resting orders are linked: when either side fills (in part or in full), the other side is automatically cancelled. Both orders sit live at the broker or platform simultaneously, and the moment one triggers, the other is pulled.

The canonical use case is a stop / take-profit bracket. Once an entry fills, you place a stop loss below entry and a take-profit target above entry, paired as an OCO group. If price runs up and hits the target, the stop is cancelled automatically — you can't accidentally end up flat and still have a resting stop trying to short the market. If price runs down and hits the stop, the target is cancelled the same way.

OCO orders exist because manual order management at speed is error-prone. Without OCO logic, you'd have to remember to cancel the other side every time one filled — and the one time you forget is the time it costs you.

Why it matters

OCO orders enforce execution hygiene automatically. They guarantee that you don't end up with orphan resting orders after an exit, which prevents a whole class of operational errors:

• Accidentally re-entering a position because a stop fired but the target was still resting and got hit on a bounce.
• Holding through a target hit because the stop was forgotten and price came back to it.
• Running scaled exits where each leg has its own bracket and needs its own automatic cleanup.

OCO is also the natural unit for bracket order templates: define entry, stop, target as a triplet, drop it on the chart, and the platform handles the rest.

How traders use it on Sierra Chart

Sierra Chart natively supports OCO order groups at the platform level. Bracket order templates can be defined with entry, stop, and target offsets, and the resulting OCO group is created automatically when the entry fills. The DOM panel and chart-attached trade panels both support sending bracketed orders in a single click.

Trade management studies extend this with more sophisticated logic — for example, OCO brackets that auto-adjust when the underlying setup changes, multiple scaled-exit legs each with their own OCO, or trail logic where the stop side of the OCO is automatically modified as price progresses.

For traders using prop firm accounts with strict order-management rules, OCO logic also helps satisfy "no orphan orders" requirements that some firms enforce.

Common patterns / pitfalls

• A modified OCO is still an OCO. Changing the stop price doesn't break the pairing — but make sure your platform actually preserves the link on edit.
• Partial fills on the entry leg need careful handling. Some setups want the OCO to scale with partial fills; others want a fixed bracket regardless.
• Cancel-replace round-trips on OCO modifications are not free — they can leave brief windows where the order isn't active. Avoid modifying OCOs during fast moves.
• Scaled exits with multiple OCO groups can produce surprising interactions when one leg fills before another expected leg. Test the behaviour in simulation before relying on it.
• OCO orders cancel — they don't reverse. If you want a stop-and-reverse, that's a different order type.

Related SCS studies

OCO logic is a platform-level execution primitive that the SCS trade-management tooling builds on rather than reimplementing. Trade Manager uses OCO brackets internally to wrap its stop and target placements so each setup ships as a self-contained, auto-managed group.