You have less time to find a fit than the non-opening side. If your suit is known to be good, partner can freely support it in the auction and lead it in defence. Plus if partner has a bad hand without support, nothing too bad can happen if you’re left in your overcall (doubled?).

Here is the Suit Quality Overcall Test, a rough-and-ready guideline (not intended to be a hard-and-fast rule), otherwise known as SQOT:

Add the number of cards in your suit (minimum number five) to the number of honours in the suit (counting one for each of the A, K, Q, J & 10) to give you your Suit Quality Count (SQC). This should get to at least as many as the tricks you’re bidding for.

Note that SQOT only applies at your first turn and that it does not mention your overall point-count. This is far less important, because your primary motivation for the bid is disruption, plus giving partner a lead. However to avoid bidding too frivolously, you should have at least six points in your hand for a one-level overcall (and eight or nine unless your suit is really good say ♠ KJ1098); and you should have at least about eight points in your hand for a two-level overcall (and 11 or 12 unless your suit is really, really good say ♣ AQJ962).

Click here to take East's Cards and defend this deal.