Williams oops

Checked October 2026

Oops buys when the market opens under yesterday's low and then trades back up through that low. Larry Williams describes it in Long-Term Secrets to Short-Term Trading, in the 1999 edition. Backtoast ran the long side on SPY. This version failed our test, losing 0.3% a year over 59 trades.

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Williams oops

The trade bets that a gap below yesterday's low fails. If SPY opens under yesterday's low, a buy stop goes at that low, so it fills only if price climbs back to it, and the trade is sold at the first open above the entry, with no stop.

The run couldn't compare a later open with the entry price, so it sold on the first trade a hair above the entry, starting a day after the buy. The book is said to add day-of-week filters, which aren't here. The volatility breakout is a different Williams rule.

The 80 20 day trade also buys back through yesterday's low.

When it works

It's a short-term mean reversion trade, so it works best in rising markets, when a gap below yesterday's low is often an overreaction that buyers reverse the same day. Traders like the clear trigger, a buy stop at yesterday's low, and the high win rate sources cite for it on S&P 500 futures. Adding a day-of-week filter, which the book is said to use, is the next thing to try, and a draft can test that before you spend a full test.

Origins

It's the section "Oops! This Is Not a Mistake" in that book, which wasn't in hand. Secondary sources cite about 81 wins in 98 S&P 500 futures trades from 1987 to 1998. The run traded SPY, long only, from late 2021 to October 2026.

The run is Backtoast's, from 29 October 2026, after costs.