Preheat oven to 400 degrees F. Line a 13 x 9 roasting pan with tinfoil and spray with cooking spray. Cut potatoes in half and then slice. Slice veggies and kielbasa.
Put a couple dabs of butter in bottom of tinfoil lined pan. Put in half the potatoes and half the veggies, sprinkle with a little minced garlic. Spread kielbasa over potato/veggie mix, then top with rest of potatoes and veggies. Put a couple more dabs of butter and a little more minced garlic. Spray another piece of tinfoil with cooking spray and put over the pan. Crimp the two pieces of tinfoil together all around so it is air tight. Poke a little hole in top.
Bake for 30 minutes, open an edge and check doneness of potatoes. Put back together and flip over for another 20-30 minutes. Open and serve!