Should You Buy Costco Stock Before Sept. 24? History Has a Clear Answer.

Costco is scheduled to report Q3 earnings after the Sept. 24 close, with analysts forecasting approximately $94.9 billion in revenue and EPS of $6.53-$6.55. The article highlights that Costco shares declined after six of its past eight quarterly reports since September 2024, with no clear post-earnings gain since June 2024. While positive on Costco's long-term fundamentals, the analysis advises waiting for results because recent post-earnings trading patterns suggest a potential opportunity to buy at a lower price.

Analysis

The relevant setup is not the reported post-earnings streak but COST's asymmetric valuation risk: a premium multiple leaves limited tolerance for any deceleration in comparable sales, renewal rates, or merchandise gross margin. A positive print that merely meets expectations can still produce multiple compression if investors infer that traffic-led growth is normalizing or that discretionary categories are weakening. In contrast, a clear upside surprise in membership-fee income or renewal-rate trajectory would be more durable than a one-quarter merchandise beat because it raises the high-margin recurring-profit base.

Near term, avoid treating a small post-report decline as a fundamental short signal; retail earnings reactions are heavily influenced by positioning and management's forward commentary on tariffs, freight, wage expense, and food deflation. Over the next 1-3 months, the key relative-value question is whether COST can defend its premium versus WMT while offering superior comp and membership-income growth. If consumer trade-down intensifies over 6-18 months, warehouse clubs should gain share from TGT and conventional grocers, but WMT is likely the cleaner beneficiary where digital fulfillment and advertising provide additional margin offsets.

The contrarian view is that cautious pre-event sentiment can make the downside less mechanical than the historical pattern implies. A post-earnings selloff becomes investable only if it is driven by transient gross-margin or FX noise while membership metrics and traffic remain intact; without those data, this is a watch item rather than a high-conviction directional trade.

Key Decisions for Investors

• Do not add to COST ahead of earnings solely on the expectation of a repeat post-report decline; the historical sample is too small and lacks controls for valuation, guidance, and market regime.
• Set a post-earnings buy alert for COST on a 7-10% decline, contingent on renewal rate stability or improvement, positive traffic, and no meaningful reduction in comp-sales or operating-margin guidance. Target a 3-6 month mean re-rating; invalidate if membership income slows materially or management cuts forward margins.
• For consumer-defensive exposure over the next 1-3 months, prefer a relative-value long WMT / short TGT basket rather than a standalone COST short. The trade benefits if value-seeking consumers remain resilient while discretionary and apparel-heavy spending weakens; cover if TGT shows sustained traffic recovery or WMT's U.S. comp guidance deteriorates.
• Monitor COST implied volatility versus its realized post-earnings move before considering options. If implied move materially exceeds the prior eight-quarter average and fundamental checks are intact, selling defined-risk downside puts after results—not before—may offer better risk-adjusted entry.