From Longman Dictionary of Contemporary Englishbe onto a good thingbe onto a good thingBritish English informalWORK HARD to have found an easy way of being successful or getting what you want Andrew knew when he was onto a good thing. → good
Examples from the Corpus
be onto a good thing• When he first invested in the company, he knew he was onto a good thing.• Many directors who take dividends in lieu of salary may think they are onto a good thing.• Maybe he thought he was onto a good thing.• Multiply that up by two or three hundred stores, and you will see he was onto a good thing.• The plots were essentially the same; like any successful entrepreneur, Alger knew when he was onto a good thing.• They felt they might be onto a good thing.• His senses told him he was onto a good thing and his senses were rarely wrong.be onto a good thingbe onto a good thinginformalPROFIT if you are onto a good thing, you are in a situation that is very helpful, comfortable, or profitable for youthink/know you are onto a good thing Directors who take dividends instead of salary may think they are onto a good thing but could have problems on retirement. → thingExamples from the Corpus
think/know you are onto a good thing• Many directors who take dividends in lieu of salary may think they are onto a good thing. 