Bridgend fought off the challenge from Builth Wells to secure the Division Two West title with a 27-19 victory over Kidwelly while the club's second and reserve sides also claimed domestic honours.
Full-back Rob Evans and wing Jonny Nation crossed while Stuart Morris added 17 points on a day of celebration.
Coles said: "We're absolutely over the moon and this is by far the greatest day in the club's history.
"We're one of the newest club's in the Welsh rugby union and we've had some ups and downs over the years with promotion and relegation.
"But for the first team to win the championship, the seconds to win the District Cup and the youth team to win the Welsh Cup on the same day is brilliant.
"It's the most successful season we've ever had and all the credit goes to the players, coaches and supporters."
Builth Wells pushed them all the way with a 25-20 home win over Mumbles.
In Division Five West, Milford Haven moved to the top of the table despite their 27-22 slip up at Furnace United.
The defeats means second-place Cefneithen are level on points but have one game remaining to clinch the championship.
Neyland grabbed the biggest win of the day with a 105-7 trouncing of bottom club Swansea Uplands while elsewhere there was also success for St Clears against Fishguard and Goodwick.






