An occasional drink is usually acceptable while taking prednisone — the UK's NHS says you can drink alcohol on this medicine — but keep it moderate, because heavy or regular drinking adds to prednisone's own tendency to irritate the stomach.
The official patient guidance does not tell you to avoid alcohol entirely — the issue is quantity, not any drinking at all. Answering this exact question, the NHS states plainly, "Yes, you can drink alcohol while taking prednisolone" (prednisolone is the UK equivalent of US prednisone, and the NHS notes prednisone and prednisolone are "very similar in terms of how well they work and how safe they are"). NHS 111 Wales adds the practical limit: "You can usually drink alcohol while taking steroid tablets, but don't drink too much as this may irritate your stomach." Prednisone is a corticosteroid whose common side effects include indigestion/stomach irritation, which is why the NHS and MedlinePlus both say to take it with food; alcohol independently irritates the stomach, so combining a lot of alcohol with prednisone can compound that. No source describes a dangerous, avoid-at-all-costs reaction (unlike, say, alcohol with metronidazole), so the honest verdict is caution/moderation, not "avoid."
Keep it moderate — NHS 111 Wales says you can usually drink but "don't drink too much as this may irritate your stomach." There is no required separation window in the sources: you do not have to time your drink hours away from your dose, but take prednisone with or after food, which the NHS and MedlinePlus both advise to reduce stomach irritation. Act urgently on signs of a stomach or pancreas problem: the NHS side-effects page says to call a doctor or 111 straight away for severe stomach pain, severe back pain, being sick, or "red or black poo," and to call 999 or go to A&E for black/dark-brown vomit or vomiting blood. Also watch for signs of high blood sugar the NHS lists — feeling very thirsty or hungry, peeing more often, or being drowsy or confused — since prednisone can raise blood glucose. Be most careful, or skip alcohol, if you have a current or past stomach ulcer or GI bleeding, take aspirin or other NSAIDs (MedlinePlus flags aspirin as interacting with prednisone), are on a high dose or a long course, or have diabetes. Call your own doctor or pharmacist before drinking if any of those apply — they can weigh your specific dose and history.
This is general reference, not medical advice, and not a guarantee of safety. Interactions depend on your doses, health conditions, and other medicines. Always confirm with your pharmacist or doctor before combining products, and follow the dosing on each label.