The two classic holiday failures: arriving at a Portuguese grill house at 21:45 to find the kitchen closing, and arriving at a Spanish one at 19:30 to find it hasn't opened. Same peninsula, opposite clocks.
TL;DR
Portugal eats earlier than Spain. PT dinner: 19:30–21:30, kitchens often stop 22:00. ES dinner: 21:00–23:00, kitchens rarely open before 20:00–20:30. Always ask: “A cozinha ainda está aberta?”
Portugal
Lunch12:30–15:00. The prato do dia (dish of the day) at lunch is the best value meal in the country. Kitchens genuinely stop around 15:00.
Dead zone15:00–19:00. Proper kitchens are closed. Cafés and pastelarias cover snacks; tourist strips serve all day (and that's part of how you spot them).
Dinner19:30–21:30 is the main service. Arriving at 19:00 as it opens is a legitimate walk-in strategy. Last orders commonly 21:30–22:00 in towns, later on resort strips.
Closing daysFamily restaurants often close Sunday night and/or Monday — the fish market's rhythm. Check before crossing town.
Coastal Spain
Lunch14:00–16:00 — the main meal of the Spanish day. Many kitchens won't take lunch orders before 13:30.
Dinner21:00–23:00. A chiringuito full of Spaniards at 22:30 is normal life, not a party. Kitchens open around 20:00–20:30.
The bridgeThe tapas bar exists partly to carry you between meal windows. Use it.
Even inside the window, a busy grill on an August night backs up: whole fish cook to order, one grill, twenty tables. If the waiter warns you the fish takes 25 minutes, that's the good sign — it means it wasn't cooked this afternoon.