Cousins took the opener 21-16, and after Burnside blazed his way to a 21-9 victory in the second, played a steady game to take the tie-breaking third set 21-14.
In the women's final, the young Alannah Stephenson beat an even younger Rachael Darragh in straight sets.
Mount Pleasant's Kirsty Kelly teamed up with Laura Butler from Wexford to win the women's doubles, beating Stephenson and partner Keady Smith.
Lisburn duo Conor Hickland and Scott Burnside beat Dublin brothers Niall and David Gannon to win the men's doubles title, while the new Leinster partnership of Ronan McGee and Norma McIntyre took the mixed title.
Paddler Fleming aims to make a splash
CANOEING: Neil Fleming of Celbridge Paddlers leads the entry at tomorrow's deferred 5km canoe national championships at Leixlip lake (11.0).
The original 5km race, due to be held in Cork last month, was cancelled due to poor weather. Fleming is already the men's K1 1,000m champion, while Kilcullen's Maria Wilmot is the women's 1,000m champion. The race follows the monthly training camp at Salmon Leap Canoe Club, Leixlip.
Recognition for Rugby League Ireland
RUGBY LEAGUE: Just days after the rugby league match against France in Thomond Park, Limerick, attracted 3,100 spectators, Rugby League Ireland has received Irish Sports Council recognition.
In the past two years, the number of clubs taking part in national competitions has grown from six to more than 20.
Perry and Blake set for Hong Kong Open
SQUASH: Irish No1 Madeline Perry faces Dipika Pallikal of India in the opening round of the Hong Kong Open, starting on Tuesday, while Irish No2 Aisling Blake faces local player Annie Au.
All-Leinster draws illuminate round two
HOCKEY: UCD host Glenanne in one of three all-Leinster draws in the second round of today's Irish Men's Hockey Cup. In the other draws, Monkstown play Pembroke, while Railway Union face Three Rock Rovers.
SNOOKER: The long journey to Letterkenny proved worthwhile for Brendan O'Donoghue, when he beat Greg Casey 5-4 to win snooker's second senior ranking tournament of the season.
TRIATHLON: Ironman Matt Molloy proved best of the Irish when he finished third over-40 at the ITU Long Distance Triathlon World Championships in Henderson, USA.