Grass Fed Burger's on the Gril

"Last night, I ate a grilled grass fed burger with sauteed arugula, cheddar cheese and tomato on a bun.  As a side I had a gouda cheese pasta salad and an edamme mushroom salad. The burger's flavor was amazing and the meat was very tender the only problem was it did not hold together very well on the grill.  Not sure why? I took the ground beef and added 1 egg, bread crumbs, salt, pepper, ketchup, mustard and worcester sauce.  Maybe I went a little too heavy on the ketchup/mustard/ worcester?  Not sure! They tasted great, but I will have to change my ratio's next time in hopes of them holding together.  No recipe, just eyed everything so maybe this is part of the problem.  The sides I bought from the grocery store.  The pasta salad had a lovely smooth gouda flavor and the edamme and mushrooms had a vinager based dressing which was nice."