We have researched all you need to know about flights between Glasgow and Dalaman, so you don't need to:
Thomas Cook Airlines (flythomascook.com) run quite regular cheap flights between Glasgow and Dalaman through most months of the year, with the exceptions of the end of October, all of November, December, January and February, and most of March. The flights take about 4 hours and 30 minutes.
The regularity of the service throughout the rest of year is quite difficult to predict. The general pattern is that there are no flights in Tuesdays and Sundays, although there are many weeks when there are indeed flights on these days, and many weeks when there is a reduced service on other days.
Thomas Cook's website (flythomascook.com) is not the best for searching dates, since the engine doesn't allow you to search with flexibility, so it's a good idea to use a price comparison website like skyscanner.net to check the best time to travel.
Because of the reasonable regularity of the service, cheap flights from Glasgow to Dalaman are not very difficult to find. As a general guide, you're likely to find one way tickets for between £90-£130 and return flights for between £180-£260, with prices towards the lesser end of that spectrum being much more common.
If it is necessary for you to travel during the aforementioned months in which Thomas Cook doesn't operate a service (October, November, December, January, February and March), you'll need to take a quite difficult and much more expensive indirect route, flying with multiple airlines via Istanbul and perhaps another European airport such as Amsterdam Schiphol or Paris Charles de Gaulle.
It's best to check a price comparison website again for this scenario, which will probably end up costing over £600 return.