If you are wondering whether to bring a caterer to your wedding venue, or use the in-house catering provided, I would suggest using onsite catering. While you might feel bringing someone else in provides you with more options, onsite catering has many more cost-efficient benefits that may not be realized right up front.
First and foremost, equipment. More times than not, the wedding venue, whether it be a country club, a restaurant, or any other Long Island wedding venue, will have all the proper equipment already for catering such a large event. This means that you won't have to rent all the necessary equipment to prepare and serve the food at your wedding. If you were to go with an outside catering company, generally you will need to rent, plates, glasses, flatware, serving utensils, a chafing dish, and linens. This unnecessary expense really adds up! Even if your local Long Island wedding venue charges you some sort of rental, or cleaning fee, it will be substantially less because they already have all this equipment in their restaurant.
The final perk to keeping with in house catering is the staff. Depending on which Long Island wedding venue you choose, you may have the option to go with buffet style or there can be a wait staff hired for table service. Whichever route you choose, it will be less expensive, and more efficient with onsite catering. The staff will be familiar with the venue. Management will know just the amount of staff to hire for the evening. And most importantly because you are using onsite catering, you won't be charged a travel fee for the staff to come to the venue. This saves so much money.
All in all, I couldn't recommend using onsite catering more. It helps keep costs down, as well as allowing the cooks, servers, and other staff work well in their familiar environment.