My bonus daughter Katie threw delicious turkey burgers together off the top of her head the other night for the grill and they were so good that I wrote down what she did:

2 lbs turkey burger
2 eggs
1 cup bread crumbs, maybe more
splashes of Worcestershire sauce
garlic powder to taste
crushed red pepper flakes (optional)
1 cup chopped onion
salt & pepper to taste

Mix and mash together, make patties, grill!

They're a little mushy and difficult to work with at the start, but that also means really moist, delicious burgers when finished!